Content

What is C ? :

What is C ?
Execution of C Program

History
Structure of C Program
Variables and Keywords :

Character Set
Identifier
Variable
Keywords
Escape Sequence Characters (Backslash Character Constants) in C

Constants :

Real Constant
Integer Constant
Character Constant
String Constant

Data Types :

Data Types
Qualifier
Enum
Typedef

Operators :

Assignment Operator
Arithmetic Operators
Logical Operators
Relational Operators
Shorthand Operators
Unary Operators
Conditional / Ternary Operator
Bitwise Operators

Operator Precedence and Associativity

Decision / Control Statements :

Decision / Control Statements
If Statement
If-Else Statement
Nested If-Else
Switch Case

Looping Statements

Looping / Iterative Statements
while
do while
for loop

Break Statement
Continue Statement
Goto
Functions :

Functions
Function call by passing value
Function call by returning value
Function call by passing and returning value
Recursion

Storage Classes :

Storage Classes
Automatic Storage Class (auto)
Register Storage Class (register)
Static Storage Class (static)
External Storage Class (extern)

Array :

Array
Single / One Dimensional Array
Two Dimensional Array

Structure :

Structure
Array in Structures
Structure with Array
Nested Structure
Difference between array and structure

Pointer
Union :

Union
Difference between structure and union

Strings
File Handling
Header Files :

Header File
Assert.h
Ctype.h
Math.h
Process.h
Stdio.h
Stdlib.h
String.h
Time.h

Programs Library

WHAT IS C ?

C language is a general purpose and structured programming language developed by 'Dennis Ritchie' at AT &T's Bell Laboratories in the 1972s in USA.

It is also called as 'Procedure oriented programming language.'

C is not specially designed for specific applications areas like COBOL (Common Business-Oriented Language) or FORTRAN (Formula Translation). It is well suited for business and scientific applications. It has some various features like control structures, looping statements, arrays, macros required for these applications.

The C language has following numerous features as:

Portability
Flexibility
Effectiveness and efficiency
Reliability
Interactivity

Execution of C Program :

C program executes in following 4 (four steps).

Creating a program :

An editor like notepad or word-pad is used to create a C program. This file contains a source code which consists of executable code. The file should be saved as '*.c' extension only.

Compiling the program :

The next step is to compile the program. The code is compiled by using compiler. Compiler converts executable code to binary code i.e. object code.

Linking a program to library :

The object code of a program is linked with libraries that are needed for execution of a program. The linker is used to link the program with libraries. It creates a file with '*.exe' extension.

Execution of program :

The final executable file is then run by dos command prompt or by any other software.

History of C :

Year of Establishment	Language Name	Developed By
1960	ALGOL-60	Cambridge University
1963	CPL (Combined Programming Language)	Cambridge University
1967	BCPL (Basic Combined Programming Language)	Martin Richard at Cambridge University
1970	B	Ken Thompson at AT & T's Bell Laboratories.
1972	C	Dennis Ritchie at AT & T' Bell Laboratory.

The development of C was a cause of evolution of programming languages like Algol 60, CPL (Combined Programming Language), BCPL (Basic Combined Programming Language) and B.

Algol-60 : (1963) :
ALGOL is an acronym for Algorithmic Language. It was the first structured procedural programming language, developed in the late 1950s and once widely used in Europe. But it was too abstract and too general structured language.
CPL : (1963) :
CPL is an acronym for Combined Programming Language. It was developed at Cambridge University.
BCPL : (1967) :
BCPL is an acronym for Basic Combined Programming Language. It was developed by Martin Richards at Cambridge University in 1967. BCPL was not so powerful. So, it was failed.
B : (1970) :
B language was developed by Ken Thompson at AT & T Bell Laboratories in 1970. It was machine dependent. So, it leads to specific problems.
C : (1972) :
'C' Programming Language was developed by Dennis Ritchie at AT & T Bell Laboratories in 1972. This is general purpose, compiled, structured programming language Dennis Ritchie studied the BCPL, then improved and named it as 'C' which is the second letter of BCPL

structure of C program

The basic structure of C program is as follow:

Document Section

Links Section (File)

Definition Section

Global variable declaration Section

void main()

{
    Variable declaration section
    Function declaration section
    executable statements;
}

Function definition 1

---------------------

Function definition n

where,

Document Section : It consists of set of comment lines which include name of a program, author name, creation date and other information.

Links Section (File) : It is used to link the required system libraries or header files to excute a program.

Definition Section : It is used to define or set values to variables.

Global variable declaration Section : It is used to declare global or public variable.

void main() : Used to start of actual C program. It includes two parts as declaration part and executable part.

Variable declaration section : Used to declare private variable.

Function declaration section : Used to declare functions of program from which we get required output.

Then, executable statements are placed for execution.

Function definition section : Used to define functions which are to be called from main().

VARIABLES AND KEYWORDS

Character Set :

A character refers to the digit, alphabet or special symbol used to data represetation.

Alphabets : A-Z, a-z
Digits : 0-9
Special Characters : ~ ! @ # $ % ^ & * ( ) _ + { } [ ] - < > , . / ? \ | : ; " '
White Spaces : Horizontal tab, Carriage return, New line, form feed

Identifier :

Identifier is the name of a variable that is made up from combination of alphabets, digits and underscore.

Variable :

It is a data name which is used to store data and may change during program execution. It is opposite to constant. Variable name is a name given to memory cells location of a computer where data is stored.

* Rules for variables:

First character should be letter or alphabet.
Keywords are not allowed to use as a variable name.
White space is not allowed.
C is case sensitive i.e. UPPER and lower case are significant.
Only underscore, special symbol is allowed between two characters.
The length of identifier may be up to 31 characters but only the first 8 characters are significant by compiler.
(Note: Some compilers allow variable names whose length may be up to 247 characters. But, it is recommended to use maximum 31 characters in variable name. Large variable name leads to occur errors.)

Keywords :

Keywords are the system defined identifiers.

All keywords have fixed meanings that do not change.

White spaces are not allowed in keywords.

Keyword may not be used as an identifier.

It is strongly recommended that keywords should be in lower case letters.

There are totally 32(Thirty Two) keywords used in a C programming.

int	float	double	long
short	signed	unsigned	const
if	else	switch	break
default	do	while	for
register	extern	static	struct
typedef	enum	return	sizeof
goto	union	auto	case
void	char	continue	volatile

Escape Sequence Characters (Backslash Character Constants) in C:

C supports some special escape sequence characters that are used to do special tasks.

These are also called as 'Backslash characters'.

Some of the escape sequence characters are as follow:

Character Constant	Meaning
\n	New line (Line break)
\b	Backspace
\t	Horizontal Tab
\f	Form feed
\a	Alert (alerts a bell)
\r	Carriage Return
\v	Vertical Tab
\?	Question Mark
\'	Single Quote
\''	Double Quote
\\	Backslash
\0	Null

Constants in C :

A constant is an entity that doesn't change during the execution of a program.

Followings are the different types of constants :

1. REAL CONSTANT :

It must have at least one digit.
It must have a decimal point which may be positive or negative.
Use of blank space and comma is not allowed between real constants.
Example:

2. INTEGER CONSTANT :

It must have at least one digit.
It should not contain a decimal place.
It can be positive or negative.
Use of blank space and comma is not allowed between real constants.
Example:

3. CHARACTER CONSTANT :

It is a single alphabet or a digit or a special symbol enclosed in a single quote.
Maximum length of a character constant is 1.
Example:

4. STRING CONSTANT :

It is collection of characters enclosed in double quotes.
It may contain letters, digits, special characters and blank space.
Example:

Data Types in C :

"Data type can be defined as the type of data of variable or constant store."

When we use a variable in a program then we have to mention the type of data. This can be handled using data type in C.

Followings are the most commonly used data types in C.

Keyword	Format Specifier	Size	Data Range
char	%c	1 Byte	-128 to +127
unsigned char	<-- -- >	8 Bytes	0 to 255
int	%d	2 Bytes	-32768 to +32767
long int	%ld	4 Bytes	-2³¹ to +2³¹
unsigned int	%u	2 Bytes	0 to 65535
float	%f	4 Bytes	-3.4e³⁸ to +3.4e³⁸
double	%lf	8 Bytes	-1.7e³⁸ to +1.7e³⁸
long double	%Lf	12-16 Bytes	-3.4e³⁸ to +3.4e³⁸

* QUALIFIER :

When qualifier is applied to the data type then it changes its size or its size.

Size qualifiers : short, long

Sign qualifiers : signed, unsigned

* ENUM DATA TYPE :

This is a user defined data type having finite set of enumeration constants. The keyword 'enum' is used to create enumerated data type.

Syntax:

enum [data_type] {const1, const2, ...., const n};

Example:

enum mca(software, web, seo);

* TYPEDEF :

It is used to create new data type. But it is commonly used to change existing data type with another name.

Syntax:

typedef [data_type] synonym;

typedef [data_type] new_data_type;

Example:

typedef int integer;
integer rno;

Operators in C :

"Operator is a symbol that is used to perform mathematical operations."

When we use a variable in a program then we have to mention the type of data. This can be handled using data type in C.

Followings are the most commonly used data types in C.

Operator Name	Operators
Assignment	=
Arithmetic	+, -, *, /, %
Logical	&&, \|\|, !
Relational	<, >, <=, >=, ==, !=
Shorthand	+=, -=, *=, /=, %=
Unary	++, --
Conditional	()?:;
Bitwise	&, \|, ^, <<, >>, ~

1. Assignment Operator

2. Arithmetic Operators

3. Logical Operators

4. Relational Operators

5. Shorthand Operators

6. Unary Operators

7. Conditional Operator

8. Bitwise Operators

Operators Precedence and Associativity :

In C, each and every operator has a special precedence which is associated with it. There are various levels of precedence. This precedence is especially used to determine to evaluation of expression which have more than one operator in it. The operators which have higher precedence are executed first and vice-versa. Operators which has same precedence level are evaluated from left to right. It is dependent on it's level. This feature is well known as 'Associativity of an operator.'

Associativity	Operator	Description
Left to Right	()	Function
	[]	Array
	-->	Pointer to member
	.	Structure

Right to left	-	Unary Minus
	+	Unary Plus
	++ / --	Increment/Decrement
	~	One's Complement
	&	Address of
	(type)	Type casting
	sizeof	Size (in bytes)
	!	Logical Not
	*	Pointer reference

Left to Right	*	Multiplication
	/	Division
	%	Modulus

Left to Right	+	Addition
Left to Right	-	Subtraction

Left to Right	<<	Left Shift
Left to Right	>>	Right Shift

Left to Right	<	Less than
	<=	Less than or equal to
	>	Greater than
	>=	Greater than or equal to

Left to Right	==	Equality
Left to Right	!=	Not Equal to

Left to Right	&	Bitwise AND

Left to Right	^	Bitwise XOR

Left to Right	\|	Bitwise OR

Left to Right	&&	Logical AND

Left to Right	\|\|	Logical OR

Left to Right	? :	Conditional Operator

Right to Left	= *= +=	Assignment

Left to Right	,	Comma

Fig.: Precedence and Associativity of operators

Decision Making Statements / Conditional Statements :

C program executes program sequentially. Sometimes, a program requires checking of certain conditions in program execution. C provides various key condition statements to check condition and execute statements according conditional criteria.

These statements are called as 'Decision Making Statements' or 'Conditional Statements.'

Followings are the different conditional statements used in C.

If Statement
If-Else Statement
Nested If-Else Statement
Switch Case

If Statement :

This is a conditional statement used in C to check condition or to control the flow of execution of statements. This is also called as 'decision making statement or control statement.' The execution of a whole program is done in one direction only.

Syntax:

if(condition)
{
	statements;
}

In above syntax, the condition is checked first. If it is true, then the program control flow goes inside the braces and executes the block of statements associated with it. If it returns false, then program skips the braces. If there are more than 1 (one) statements in if statement then use { } braces else it is not necessary to use.

Program :

/*  Program to demonstrate if statement */

#include <stdio.h>
#include <conio.h>
void main()
{
	int a;
	a=5;
	clrscr();
	if(a>4)
		printf("\nValue of A is greater than 4 !");
	if(a==4)
		printf("\n\n Value of A is 4 !");
	getch();
}

Output :

Value of A is greater than 4 !_

If-Else Statement :

This is also one of the most useful conditional statement used in C to check conditions.

Syntax:

if(condition)
{
	true statements;
}
else
{
	false statements;
}

Program :

/*  Program to demonstrate if-else statement */

#include <stdio.h>
#include <conio.h>
void main()
{
	int no;
	clrscr();
	printf("\n Enter Number :");
	scanf("%d",&no);
	if(no%2==0)
		printf("\n\n Number is even !");
	else
		printf("\n\n Number is odd !");
	getch();
}

Output :

Enter Number : 11

Number is odd !_

Switch case Statement :

This is a multiple or multiway bracing decision making statement.

When we use nested if-else statement to check more than 1 condition then the complexity of a program increases in case of a lot of conditions. Thus, the program is difficult to read and maintain. So to overcome this problem, C provides 'switch case'.

Switch case checks the value of a expression against a case values, if condition matches the case values then the control is transferred to that point.

Syntax:

switch(expression)
{
	case expr1:
		statements;
		break;
	case expr2:
		statements;
		break;

        ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' 
        ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' 

	case exprn:
		statements;
		break;						
	default:
		statements;
}

In above syntax, switch, case, break are keywords.

expr1, expr2 are known as 'case labels.'

Statements inside case expression need not to be closed in braces.

Break statement causes an exit from switch statement.

Default case is optional case. When neither any match found, it executes.

Program :

/*  Program to demonstrate switch case statement */

#include <stdio.h>
#include <conio.h>
void main()
{
	int no;
	clrscr();
	printf("\n Enter any number from 1 to 3 :");
	scanf("%d",&no);
	switch(no)
	{
		case 1:
			printf("\n\n It is 1 !");
			break;
		case 2:
			printf("\n\n It is 2 !");
			break;
		case 3:
			printf("\n\n It is 3 !");
			break;
		default:
			printf("\n\n Invalid number !");
	}
	getch();
}

Output 1 :

Enter any number from 1 to 3 : 3

It is 3 !_

Output 2 :

Enter any number from 1 to 3 : 5

Invalid number !_

* RULES FOR DECLARING SWITCH CASE :

The case label should be integer or character constant.
Each compound statement of a switch case should contain break statement to exit from case.
Case labels must end with (:) colon.

* ADVANTAGES OF SWITCH CASE :

Easy to use.
Easy to find out errors.
Debugging is made easy in switch case.
Complexity of a program is minimized.

Nested If-Else Statement :

It is a conditional statement which is used when we want to check more than 1 condition at a time in a same program. The conditions are executed from top to bottom checking each condition whether it meets the conditional criteria or not. If it found the condition is true then it executes the block of associated statements of true part else it goes to next condition to execute.

Syntax:

if(condition)
{
	if(condition)
	{
		statements;
	}
	else
	{
		statements;
	}
}
else
{
	statements;
}

In above syntax, the condition is checked first. If it is true, then the program control flow goes inside the braces and again checks the next condition. If it is true then it executes the block of statements associated with it else executes else part.

Program :

/*  Program to demonstrate nested if-else statement */

#include <stdio.h>
#include <conio.h>
void main()
{
	int no;
	clrscr();
	printf("\n Enter Number :");
	scanf("%d",&no);
	if(no>0)
	{
		printf("\n\n Number is greater than 0 !");
	}
	else
	{
		if(no==0)
		{
			printf("\n\n It is 0 !");
		}
		else
		{
			printf("Number is less than 0 !");
		}
	}
	getch();
}

Output :

Enter Number : 0

It is 0 !_

Looping Statements / Iterative Statements :

'A loop' is a part of code of a program which is executed repeatedly.

A loop is used using condition. The repetition is done until condition becomes condition true.

A loop declaration and execution can be done in following ways.

Check condition to start a loop
Initialize loop with declaring a variable.
Executing statements inside loop.
Increment or decrement of value of a variable.

* TYPES OF LOOPING STATEMENTS :

Basically, the types of looping statements depend on the condition checking mode. Condition checking can be made in two ways as : Before loop and after loop. So, there are 2(two) types of looping statements.

Entry controlled loop
Exit controlled loop

1. Entry controlled loop :

In such type of loop, the test condition is checked first before the loop is executed.

Some common examples of this looping statements are :

while loop
for loop

While loop :

This is an entry controlled looping statement. It is used to repeat a block of statements until condition becomes true.

Syntax:

while(condition)
{
	statements;
	increment/decrement;
}

In above syntax, the condition is checked first. If it is true, then the program control flow goes inside the loop and executes the block of statements associated with it. At the end of loop increment or decrement is done to change in variable value. This process continues until test condition satisfies.

Program :

/*  Program to demonstrate while loop */

#include <stdio.h>
#include <conio.h>
void main()
{
	int a;
	clrscr();
	a=1;
	while(a<=5)
	{
		printf("\n TechnoExam");
		a+=1      // i.e. a = a + 1
	}
	getch();
}

Output :

 TechnoExam
 TechnoExam
 TechnoExam
 TechnoExam
 TechnoExam_

For loop :

This is an entry controlled looping statement.

In this loop structure, more than one variable can be initilized. One of the most important feature of this loop is that the three actions can be taken at a time like variable initilisation, condition checking and increment/decrement. The for loop can be more concise and flexible than that of while and do-while loops.

Syntax:

for(initialisation; test-condition; incre/decre)
{
	statements;
}

In above syntax, the given three expressions are separated by ';' (Semicolon)

Features :

More concise
Easy to use
Highly flexible
More than one variable can be initialized.
More than one increment can be applied.
More than two conditions can be used.

Program :

/*  Program to demonstrate for loop */

#include <stdio.h>
#include <conio.h>
void main()
{
	int a;
	clrscr();
	for(i=0; i<5; i++)
	{
		printf("\n\t TechnoExam");  // 5 times
	}
	getch();
}

Output :

	TechnoExam
	TechnoExam
	TechnoExam
	TechnoExam
	TechnoExam_

2. Exit controlled loop :

In such type of loop, the loop is executed first. Then condition is checked after block of statements are executed. The loop executed atleat one time compulsorily.

Some common example of this looping statement is :

do-while loop

Do-While loop :

This is an exit controlled looping statement.

Sometimes, there is need to execute a block of statements first then to check condition. At that time such type of a loop is used. In this, block of statements are executed first and then condition is checked.

Syntax:

do
{
	statements;
	(increment/decrement);
}while(condition);

In above syntax, the first the block of statements are executed. At the end of loop, while statement is executed. If the resultant condition is true then program control goes to evaluate the body of a loop once again. This process continues till condition becomes true. When it becomes false, then the loop terminates.

Note: The while statement should be terminated with ; (semicolon).

Program :

/*  Program to demonstrate do while loop */

#include <stdio.h>
#include <conio.h>
void main()
{
	int a;
	clrscr();
	a=1;
	do
	{
		printf("\n\t TechnoExam");  // 5 times
		a+=1;      // i.e. a = a + 1
	}while(a<=5);
	a=6;
	do
	{
		printf("\n\n\t Technowell");  // 1 time
		a+=1;      // i.e. a = a + 1
	}while(a<=5);
	getch();
}

Output :

 TechnoExam
 TechnoExam
 TechnoExam
 TechnoExam
 TechnoExam
 
 Technowell_

Break Statement :

Sometimes, it is necessary to exit immediately from a loop as soon as the condition is satisfied.

When break statement is used inside a loop, then it can cause to terminate from a loop. The statements after break statement are skipped.

Syntax :

	break;

Figure :

Program :

/*  Program to demonstrate break statement */

#include <stdio.h>
#include <conio.h>
void main()
{
	int i;
	clrscr();
	for(i=1;  ; i++)
	{
		if(i>5)
		break;
		printf("%d",i);  // 5 times only
	}
	getch();
}

Output :

12345_

Continue Statement :

Sometimes, it is required to skip a part of a body of loop under specific conditions. So, C supports 'continue' statement to overcome this anomaly.

The working structure of 'continue' is similar as that of that break statement but difference is that it cannot terminate the loop. It causes the loop to be continued with next iteration after skipping statements in between. Continue statement simply skipps statements and continues next iteration.

Syntax :

	continue;

Figure :

Program :

/*  Program to demonstrate continue statement */

#include <stdio.h>
#include <conio.h>
void main()
{
	int i;
	clrscr();
	for(i=1; i<=10; i++)
	{
		if(i==6)
		continue;
		printf("\n\t %d",i);  // 6 is omitted
	}
	getch();
}

Output :

Goto Statement :

It is a well-known as 'jumping statement.' It is primarily used to transfer the control of execution to any place in a program. It is useful to provide branching within a loop.

When the loops are deeply nested at that if an error occurs then it is difficult to get exited from such loops. Simple break statement cannot work here properly. In this situations, goto statement is used.

Syntax :

	goto [expr];

Figure :

Program :

/*  Program to demonstrate goto statement */

#include <stdio.h>
#include <conio.h>
void main()
{
	int i=1, j;
	clrscr();
	while(i<=3)
	{
		for(j=1; j<=3; j++)
		{
			printf(" * ");
			if(j==2)
			goto stop;
		}
		i = i + 1;
	}
	stop:
		printf("\n\n Exited !");
	getch();
}

Output :

 *  *

 Exited_

FUNCTIONS

Functions in C :

The function is a self-contained block of statements which performs a coherent task of a same kind.

C program does not execute the functions directly. It is required to invoke or call that functions. When a function is called in a program then program control goes to the function body. Then, it executes the statements which are involved in a function body. Therefore, it is possible to call function whenever we want to process that functions statements.

Types of functions :

There are 2(two) types of functions as:

1. Built in Functions
2. User Defined Functions

1. Built in Functions :

These functions are also called as 'library functions'. These functions are provided by system. These functions are stored in library files. e.g.

scanf()
printf()
strcpy
strlwr
strcmp
strlen
strcat

2. User Defined Functions :

The functions which are created by user for program are known as 'User defined functions'.

Syntax:

void main()
{
	// Function prototype
	<return_type><function_name>([<argu_list>]);
	
	// Function Call
	<function_name>([<arguments>]);
}
// Function definition
<return_type><function_name>([<argu_list>]);
{
	<function_body>;
}

Program :

/*  Program to demonstrate function */

#include <stdio.h>
#include <conio.h>

void add()
{
	int a, b, c;
	clrscr();
	printf("\n Enter Any 2 Numbers : ");
	scanf("%d %d",&a,&b);
	c = a + b;
	printf("\n Addition is : %d",c);
}
void main()
{
	void add();
	add();
	getch();
}

Output :

 Enter Any 2 Numbers : 23 6
 Addition is : 29_

* Function Call By Passing Value

When a function is called by passing value of variables then that function is known as 'function call by passing values.'

Syntax:

// Declaration
void <function_name>(<data_type><var_nm>)

// Calls
<function_name>(<var_nm>);

// Definition
void <function_name>(<data_type><var_nm>)
{
	<function_body>;
	- - - - - - - -;
}

Program :

/*  Program to demonstrate function call by passing value */

#include <stdio.h>
#include <conio.h>

void printno(int a)
{
	printf("\n Number is : %d", a);
}
void main()
{
	int no;
	void printno(int);
	clrscr();
	printf("\n Enter Number : ");
	scanf("%d", &no);
	printno(no);
	getch();
}

Output :

 Enter Number : 21
 
 Number is : 21_

* Function Call By Returning Value

When a function returns value of variables then that function is known as 'function call by returning values.'

Syntax:

// Declaration
<data_type><function_name>();

// Calls
<variable_of_function>=<function_nm>();

// Definition
<data_type><function_name>()
{
	<function_body>;
	- - - - - - - -;
	return <variable_of_function>;
}

Program :

/* Program to demonstrate function call by returning value */

#include <stdio.h>
#include <conio.h>

int number()
{
	int no;
	printf("\n Enter Number : ");
	scanf("%d",&no);
	return no;
}
void main()
{
	int no;
	int number();
	clrscr();
	no = number();
	printf("\n Number is : %d",no);
	getch();
}

Output :

 Enter Number : 5
 
 Number is : 5_

* Function Call By Passing and Returning Value

When a function passes and returns value of variables then that function is known as 'function call by passing and returning values.'

Program :

/* Program to demonstrate function call by passing 

and returning value */

#include <stdio.h>
#include <conio.h>

int number(int n)
{
	return n;
}
void main()
{
	int number(int);
	int a = number(4);
	clrscr();
	printf("\n Number is : %d",a);
	getch();
}

Output :

 Number is : 4_

Advantages :

It is easy to use.
Debugging is more suitable for programs.
It reduces the size of a program.
It is easy to understand the actual logic of a program.
Highly suited in case of large programs.
By using functions in a program, it is possible to construct modular and structured programs.

* Recursion (Recursive Function)

When a function of body calls the same function then it is called as 'recursive function.'

Example:

Recursion()
{
	printf("Recursion !");
	Recursion();
}

Program :

/* Program to demonstrate function recursion */

#include <stdio.h>
#include <conio.h>

Recursion()
{
	int no;
	printf("\nRecursion... ");
	printf("\n\n Enter Number : ");
	scanf("%d",&no);
	if (no==3)
		exit(0);
	else
		Recursion();
}
void main()
{
	clrscr();
	Recursion();
}

Output :

Recursion...

 Enter Number : 2

Recursion...

 Enter Number : 1

Recursion...

 Enter Number : 3_

Features :

There should be at least one if statement used to terminate recursion.
It does not contain any looping statements.

Advantages :

It is easy to use.
It represents compact programming structures.

Disadvantages :

It is slower than that of looping statements because each time function is called.

Note :

It can be applied to calculate factorial of a number, Fibonacci series.

Storage Class :

'Storage' refers to the scope of a variable and memory allocated by compiler to store that variable. Scope of a variable is the boundary within which a variable can be used. Storage class defines the the scope and lifetime of a variable.

From the point view of C compiler, a variable name identifies physical location from a computer where variable is stored. There are two memory locations in a computer system where variables are stored as : Memory and CPU Registers.

Functions of storage class :

To determine the location of a variable where it is stored ?

Set initial value of a variable or if not specified then setting it to default value?

Defining scope of a variable?

To determine the life of a variable?

Types of Storage Classes :

Storage classes are categorized in 4 (four) types as,

Automatic Storage Class
Register Storage Class
Static Storage Class
External Storage Class

Automatic Storage Class :

Keyword : auto
Storage Location : Main memory
Initial Value : Garbage Value
Life : Control remains in a block where it is defined.
Scope : Local to the block in which variable is declared.

Syntax :

	auto [data_type] [variable_name];

Example :

	auto int a;

Program :

/*  Program to demonstrate automatic storage class */

#include <stdio.h>
#include <conio.h>
void main()
{
	auto int i=10;
	clrscr();
	{
		auto int i=20;
		printf("\n\t %d",i);
	}
	printf("\n\n\t %d",i);
	getch();
}

Output :

	20

	10_

Static Storage Class :

Keyword : static
Storage Location : Main memory
Initial Value : Zero and can be initialize once only.
Life : depends on function calls and the whole application or program.
Scope : Local to the block.

Syntax :

	static [data_type] [variable_name];

Example :

	static int a;

There are two types of static variables as :

a) Local Static Variable
b) Global Static Variable

Static storage class can be used only if we want the value of a variable to persist between different function calls.

Program :

/*  Program to demonstrate static storage class */

#include <stdio.h>
#include <conio.h>

void main()
{
	int i;
	void incre(void);
	clrscr();
	for (i=0; i<3; i++)
	incre();
	getch();
}

void incre(void)
{
	int avar=1;
	static int svar=1;
	avar++;
	svar++;
	printf("\n\n Automatic variable value : %d",avar);
	printf("\t Static variable value : %d",svar);
}

Output :

Automatic variable value : 2	Static variable value : 2

Automatic variable value : 2	Static variable value : 3

Automatic variable value : 2	Static variable value : 4_

External Storage Class :

Keyword : extern
Storage Location : Main memory
Initial Value : Zero
Life : Until the program ends.
Scope : Global to the program.

Syntax :

	extern [data_type] [variable_name];

Example :

	extern int a;

The variable access time is very fast as compared to other storage classes. But few registers are available for user programs.

The variables of this class can be referred to as 'global or external variables.' They are declared outside the functions and can be invoked at anywhere in a program.

Program :

/*  Program to demonstrate external storage class */

#include <stdio.h>
#include <conio.h>

extern int i=10;
void main()
{
	int i=20;
	void show(void);
	clrscr();
	printf("\n\t %d",i);
	show();
	getch();
}
void show(void)
{
	printf("\n\n\t %d",i);
}

Output :

	20

	10_

Array :

Array is a collection of homogeneous data stored under unique name. The values in an array is called as 'elements of an array.' These elements are accessed by numbers called as 'subscripts or index numbers.' Arrays may be of any variable type.

Array is also called as 'subscripted variable.'

Types of an Array :

Single / One Dimensional Array :

The array which is used to represent and store data in a linear form is called as 'single or one dimensional array.'

Syntax:

	<data-type> <array_name> [size];

Example:

	int a[3] = {2, 3, 5};
	char ch[20] = "Techno Exam" ;
	float stax[3] = {5003.23, 1940.32, 123.20} ;
	
Total Size (in Bytes):

	total size = length of array * size of data type

In above example, a is an array of type integer which has storage size of 3 elements. The total size would be 3 * 2 = 6 bytes.

* MEMORY ALLOCATION :

	    
    Fig : Memory allocation for one dimensional array

Program :

/*  Program to demonstrate one dimensional array */

#include <stdio.h>
#include <conio.h>
void main()
{
	int a[3], i;;
	clrscr();
	printf("\n\t Enter three numbers : ");
	for(i=0; i<3; i++)
	{
		scanf("%d", &a[i]);  // read array
	}
	printf("\n\n\t Numbers are : ");
	for(i=0; i<3; i++)
	{
		printf("\t %d", a[i]);  // print array
	}
	getch();
}

Output :

	Enter three numbers : 9 4 6
	
	Numbers are :	9	4	6_

Features :

Array size should be positive number only.
String array always terminates with null character ('\0').
Array elements are countered from 0 to n-1.
Useful for multiple reading of elements (numbers).

Disadvantages :

There is no easy method to initialize large number of array elements.
It is difficult to initialize selected elements.

Two Dimensional Array :

The array which is used to represent and store data in a tabular form is called as 'two dimensional array.' Such type of array specially used to represent data in a matrix form.

The following syntax is used to represent two dimensional array.

Syntax:

<data-type> <array_nm> [row_subscript][column-subscript];

Example:

	int a[3][3];

In above example, a is an array of type integer which has storage size of 3 * 3 matrix. The total size would be 3 * 3 * 2 = 18 bytes.

It is also called as 'multidimensional array.'

* MEMORY ALLOCATION :

	    
    Fig : Memory allocation for two dimensional array

Program :

/*  Program to demonstrate two dimensional array */

#include <stdio.h>
#include <conio.h>
void main()
{
	int a[3][3], i, j;
	clrscr();
	printf("\n\t Enter matrix of 3*3 : ");
	for(i=0; i<3; i++)
	{
		for(j=0; j<3; j++)
		{
		scanf("%d",&a[i][j]);  //read 3*3 array
		}
	}
	printf("\n\t Matrix is : \n");
	for(i=0; i<3; i++)
	{
		for(j=0; j<3; j++)
		{
		printf("\t %d",a[i][j]);  //print 3*3 array
		}
	   printf("\n");
	}
	getch();
}

Output :

	Enter matrix of 3*3 : 3 4 5 6 7 2 1 2 3
	
	Matrix is :
	3	4	5
	6	7	2
	1	2	3_

Limitations of two dimensional array :

We cannot delete any element from an array.
If we dont know that how many elements have to be stored in a memory in advance, then there will be memory wastage if large array size is specified.

STRUCTURES

Structure :

Structure is user defined data type which is used to store heterogeneous data under unique name. Keyword 'struct' is used to declare structure.

The variables which are declared inside the structure are called as 'members of structure'.

Syntax:

struct structure_nm
{
	<data-type> element 1;
	<data-type> element 2;
	- - - - - - - - - - -
	- - - - - - - - - - -
	<data-type> element n;
}struct_var;


Example :

struct emp_info
{
	char emp_id[10];
	char nm[100];
	float sal;
}emp;

Note :

1. Structure is always terminated with semicolon (;).

2. Structure name as emp_info can be later used to declare structure variables of its type in a program.

* INSTANCES OF STRUCTURE :

Instances of structure can be created in two ways as,

Instance 1:

struct emp_info
{
	char emp_id[10];
	char nm[100];
	float sal;
}emp;


Instance 2:

struct emp_info
{
	char emp_id[10];
	char nm[100];
	float sal;
};
struct emp_info emp;

In above example, emp_info is a simple structure which consists of structure members as Employee ID(emp_id), Employee Name(nm), Employee Salary(sal).

* ACCESSING STRUCTURE MEMBERS :

Structure members can be accessed using member operator '.' . It is also called as 'dot operator' or 'period operator'.

structure_var.member;

Program :

/*  Program to demonstrate structure */

#include <stdio.h>
#include <conio.h>

struct comp_info
{
	char nm[100];
	char addr[100];
}info;

void main()
{
	clrscr();
	printf("\n Enter Company Name : ");
	gets(info.nm);
	printf("\n Enter Address : ");
	gets(info.addr);
	printf("\n\n Company Name : %s",info.nm);
	printf("\n\n Address : %s",info.addr);
	getch();
}

Output :

 Enter Company Name : TechnoExam, Technowell Web Solutions
 Enter Address : Sangli, Maharashtra, INDIA
 
 Company Name : TechnoExam, Technowell Web Solutions
 Address : Sangli, Maharashtra, INDIA_

Array in Structures :

Sometimes, it is necessary to use structure members with array.

Program :

/*  Program to demonstrate array in structures */

#include <stdio.h>
#include <conio.h>

struct result
{
	int rno, mrks[5];
	char nm;
}res;

void main()
{
	int i,total;
	clrscr();
	total = 0;
	printf("\n\t Enter Roll Number : ");
	scanf("%d",&res.rno);
	printf("\n\t Enter Marks of 3 Subjects : ");
	for(i=0;i<3;i++)
	{
		scanf("%d",&res.mrks[i]);
		total = total + res.mrks[i];
	}
	printf("\n\n\t Roll Number : %d",res.rno);
	printf("\n\n\t Marks are :");
	for(i=0;i<3;i++)
	{
		printf(" %d",res.mrks[i]);
	}
	printf("\n\n\t Total is : %d",total);
	getch();
}

Output :

	Enter Roll Number : 1
	
	Enter Marks of 3 Subjects : 63 66 68
	
	
	Roll Number : 1
	
	Marks are : 63 66 68
	
	Total is : 197_

Structure With Array :

We can create structures with array for ease of operations in case of getting multiple same fields.

Program :

/*  Program to demonstrate Structure With Array */

#include <stdio.h>
#include <conio.h>

struct emp_info
{
	int emp_id;
	char nm[50];
}emp[2];

void main()
{
	int i;
	clrscr();
	for(i=0;i<2;i++)
	{
		printf("\n\n\t Enter Employee ID : ");
		scanf("%d",&emp[i].emp_id);
		printf("\n\n\t Employee Name : ");
		scanf("%s",emp[i].nm);
	}
	for(i=0;i<2;i++)
	{
	   printf("\n\t Employee ID : %d",emp[i].emp_id);
	   printf("\n\t Employee Name : %s",emp[i].nm);
	}
	getch();
}

Output :

	Enter Employee ID : 1
	
	Employee Name : ABC
	
	Enter Employee ID : 2
	
	Employee Name : XYZ
	
	Employee ID : 1
	Employee Name : ABC
	Employee ID : 2
	Employee Name : XYZ_

Structures within Structures (Nested Structures) :

Structures can be used as structures within structures. It is also called as 'nesting of structures'.

Syntax:

struct structure_nm
{
	<data-type> element 1;
	<data-type> element 2;
	- - - - - - - - - - -
	- - - - - - - - - - -
	<data-type> element n;
	
	struct structure_nm
	{
		<data-type> element 1;
		<data-type> element 2;
		- - - - - - - - - - -
		- - - - - - - - - - -	
		<data-type> element n;
	}inner_struct_var;
}outer_struct_var;


Example :

struct stud_Res
{
	int rno;
	char nm[50];
	char std[10];
	
	struct stud_subj
	{
		char subjnm[30];
		int marks;
	}subj;
}result;

In above example, the structure stud_Res consists of stud_subj which itself is a structure with two members. Structure stud_Res is called as 'outer structure' while stud_subj is called as 'inner structure.' The members which are inside the inner structure can be accessed as follow :

result.subj.subjnm
result.subj.marks

Program :

/*  Program to demonstrate nested structures */

#include <stdio.h>
#include <conio.h>

struct stud_Res
{
	int rno;
	char std[10];
	struct stud_Marks
	{
		char subj_nm[30];
		int subj_mark;
	}marks;
}result;

void main()
{
	clrscr();
	printf("\n\t Enter Roll Number : ");
	scanf("%d",&result.rno);
	printf("\n\t Enter Standard : ");
	scanf("%s",result.std);
	printf("\n\t Enter Subject Code : ");
	scanf("%s",result.marks.subj_nm);
	printf("\n\t Enter Marks : ");
	scanf("%d",&result.marks.subj_mark);
	printf("\n\n\t Roll Number : %d",result.rno);
	printf("\n\n\t Standard : %s",result.std);
	printf("\nSubject Code : %s",result.marks.subj_nm);
	printf("\n\n\t Marks : %d",result.marks.subj_mark);
	getch();
}

Output :

	Enter Roll Number : 1
	
	Enter Standard : MCA(Sci)-I
	
	Enter Subject Code : SUB001
	
	Enter Marks : 63
	
	
	Roll Number : 1
	
	Standard : MCA(Sci)-I
Subject Code : SUB001

	Marks : 63_

Pointer :

Pointer is a variable which holds the memory address of another variable. Pointers are represented by '*'. It is a derive data type in C. Pointer returns the value of stored address.

Syntax:

	<data_type> *pointer_name;

In above syntax,
* = variable pointer_name is a pointer variable.
pointer_name requires memory location
pointer_name points to a variable of type data type.

How to Use ?
	
	int *tot;

Illustration :

	int tot = 95;
	
Figure :

In above example, the statement instructs the system to find out a location for integer variable quantity and puts the values 95 in that memory location.

* Features of Pointer :

* Pointer variable should have prefix '*'.

* Combination of data types is not allowed.

* Pointers are more effective and useful in handling arrays.

* It can also be used to return multiple values from a function using function arguments.

* It supports dynamic memory management.

* It reduces complexity and length of a program.

* It helps to improve execution speed that results in reducing program execution time.

Program :

/*  Program to demonstrate pointer */

#include <stdio.h>
#include <conio.h>

void main()
{
	int a=10;
	int *ptr;
	clrscr();
	ptr = &a;
	printf("\n\t Value of a : %d", a);
	scanf("\n\n\t Value of pointer ptr : %d", *ptr);
	printf("\n\n\t Address of pointer ptr : %d", ptr);
	getch();
}

Output :

	Value of a : 10
	
	Value of pointer ptr : 10
	
	Address of pointer ptr : -12_

Union :

Union is user defined data type used to stored data under unique variable name at single memory location.

Union is similar to that of structure. Syntax of union is similar to structure. But the major difference between structure and union is 'storage.' In structures, each member has its own storage location, whereas all the members of union use the same location. Union contains many members of different types, it can handle only one member at a time.

To declare union data type, 'union' keyword is used.

Union holds value for one data type which requires larger storage among their members.

Syntax:

	union union_name
	{
		<data-type> element 1;
		<data-type> element 2;
		<data-type> element 3;
	}union_variable;

Example:

	union techno
	{
		int comp_id;
		char nm;
		float sal;
	}tch;

In above example, it declares tch variable of type union. The union contains three members as data type of int, char, float. We can use only one of them at a time.

* MEMORY ALLOCATION :

	    
	 Fig : Memory allocation for union

To access union members, we can use the following syntax.

	tch.comp_id
	tch.nm
	tch.sal

Program :

/*  Program to demonstrate union */

#include <stdio.h>
#include <conio.h>

union techno
{
	int id;
	char nm[50];
}tch;


void main()
{
	clrscr();
	printf("\n\t Enter developer id : ");
	scanf("%d", &tch.id);
	printf("\n\n\t Enter developer name : ");
	scanf("%s", tch.nm);
	printf("\n\n Developer ID : %d", tch.id);//Garbage 
	printf("\n\n Developed By : %s", tch.nm);
	getch();
}

Output :

	Enter developer id : 101
	
	Enter developer name : technowell
	
Developer ID : 25972

Developed By : technowell_

String Handling in C :

String :

A string is a collection of characters. Strings are always enclosed in double quotes as "string_constant".

Strings are used in string handling operations such as,

Counting the length of a string.
Comparing two strings.
Copying one string to another.
Converting lower case string to upper case.
Converting upper case string to lower case.
Joining two strings.
Reversing string.

Declaration :

The string can be declared as follow :

Syntax:

	char string_nm[size];

Example:

	char name[50];

String Structure :

When compiler assigns string to character array then it automatically supplies null character ('\0') at the end of string. Thus, size of string = original length of string + 1.

	char name[7];
	name = "TECHNO"

Read Strings :

To read a string, we can use scanf() function with format specifier %s.

	char name[50];
	scanf("%s",name);

The above format allows to accept only string which does not have any blank space, tab, new line, form feed, carriage return.

Write Strings :

To write a string, we can use printf() function with format specifier %s.

	char name[50];
	scanf("%s",name);
	printf("%s",name);

String handling functions :

string.h header file :

'string.h' is a header file which includes the declarations, functions, constants of string handling utilities. These string functions are widely used today by many programmers to deal with string operations.

Some of the standard member functions of string.h header files are,

Function Name	Description
strlen -	Returns the length of a string.
strlwr -	Returns upper case letter to lower case.
strupr -	Returns lower case letter to upper case.
strcat -	Concatenates two string.
strcmp -	Compares two strings.
strrev -	Returns length of a string.
strcpy -	Copies a string from source to destination.

Program :

/*  Program to demonstrate string.h header file working */

#include <stdio.h>
#include <conio.h>
#include <string.h>
void main()
{
	char str[50];
	clrscr();
	printf("\n\t Enter your name : ");
	gets(str);
	printf("\nLower case of string: %s",strlwr(str));
	printf("\nUpper case of string: %s",strupr(str));
	printf("\nReverse of string: %s",strrev(str));
	printf("\nLength of String: %d",strlen(str));
	getch();
}

Output :

	Enter your name : Technoexam
Lower case of string: technoexam
Upper case of string: TECHNOEXAM
Reverse of string: MAXEONHCET	
Length of String: 10_

HEADER FILE

Header File in C :

Header file contains different predefined functions, which are required to run the program. All header files should be included explicitly before main ( ) function.

It allows programmers to separate functions of a program into reusable code or file. It contains declarations of variables, subroutines. If we want to declare identifiers in more than one source code file then we can declare such identifiers in header file. Header file has extension like '*.h'. The prototypes of library functions are gathered together into various categories and stored in header files.

E.g. All prototypes of standard input/output functions are stored in header file 'stdio.h' while console input/output functions are stored in 'conio.h'.

The header files can be defined or declared in two ways as

Method 1 : #include "header_file-name"
Method 2 : #include <header_file-name>

Method 1 is used to link header files in current directory as well as specified directories using specific path. The path must be up to 127 characters. This is limit of path declaration. Method 2 is used to link header files in specified directories only.

Standard Header Files :

Followings are the some commonly used header files which plays a vital role in C programming :

Assert.h	Ctype.h	Math.h
Process.h	Stdio.h	Stdlib.h
String.h	Time.h	Graphics.h

assert.h header file :

assert.h is a header file which defines C preprocessor macro as assert(). Macro uses assertion which is used to verify conditions or assumptions in a program. It prints message when it returns false.

The use of assert() can be defined as follow :

Program :

/*  Program to demonstrate assert.h header file working */

#include <stdio.h>
#include <conio.h>
#include <assert.h>
void main()
{
	clrscr();
	assert(12 == 2);
	getch();
}

Output :

Assertion failed: 12==2, file ..\ASSERT.C, line 5
Abnormal program termination
_

ctype.h (Character Functions header file):

It contains the declarations for character functions i.e. it contains information used by the character classification and character conversion macros.

Some of the standard member functions of ctype.h header files are,

Function Name	Description
isalnum -	checks for alphanumeric character.
isalpha -	checks for alphabetic character.
isxdigit -	checks for hexadecimal digit.
isupper -	checks for upper case character.
isspace -	checks for any whitespace character.
ispunct -	checks for punctuation character.
isdigit -	checks for digits.
islower -	checks for lower case characters.
isprint -	checks for printable character with space character.
isgraph -	checks for graphic character without space character.

Example :

/*  Program to demonstrate ctype.h header file working */

#include <stdio.h>
#include <conio.h>
#include <ctype.h>
#include <string.h>
void main()
{
	int len, i;
	char *str = "MICROSOFT";
	clrscr();
	len = strlen(str);
	for(i=1;i<=len;i++)
	{
		str[i] = tolower(str[i]); //tolower()
	}
	printf("\n\t Using tolower() : %s"<,str);
	for(i=1;i<=len;i++)
	{
		str[i] = toupper(str[i]); //toupper()
	}
	printf("\n\n\t Using toupper() : %s",str);
	getch();
}

Output :

	Using tolower() : microsoft


	Using toupper() : MICROSOFT_

math.h header file :

math.h is a header file which is commonly used for mathematical operations. Some functions of this header file uses floating point numbers. The functions which accepts angle are accepted in terms of radians.

Some of the standard member functions of math.h header files are,

Function Name	Description
acos -	Arccosine - Returns inverse cosine.
cos -	Returns cosine.
log -	Returns log of a number.
pow(x,y) -	Returns power of x raise to y. i.e. x^y
sqrt -	Returns square root of a number.
tan -	Returns tangent.
ceil -	Ceiling - Small int not less than that of parameter.
exp -	Uses as an Exponential function.
floor -	Floor - Largest int not greater than parameter.

Program :

/*  Program to demonstrate math.h header file working */

#include <stdio.h>
#include <conio.h>
#include <math.h>
void main()
{
	clrscr();
	printf("\n\t Log of 10 : %f",log(10));
	printf("\n\n\t Square Root of 16 : %f",sqrt(16));
	printf("\n\n\t Square of 4 : %f",pow(4,2));
	printf("\n\n\t Sine of 10 : %f",sin(10));
	getch();
}

Output :

	Log of 10 : 2.302585

	Square Root of 16 : 4.000000

	Square of 4 : 16.000000

	Sine of 10 : -0.544021_

process.h header file :

'process.h' is a header file which includes macros and declarations. These are especially used during work with thread and processes. There is no standard for process.h functions. They depend on compiler which we use.

Some of the standard member functions of process.h header files are,

Function Name	Description
execle -	It loads & executes new child process by placing it in memory previously occupied by the parent process.
spawnv -	Parameters are passed as an array of pointers. It loads & executes new child process.
getpid -	It returns the process identifier.
execlp -	It loads & executes a new child process by placing it in memory previously occupied by the parent process.

Program :

/*  Program to demonstrate process.h header file working */

#include <stdio.h>
#include <conio.h>
#include <process.h>
void main()
{
	clrscr();
	// under DOS PSP segment
	printf("\n\t Program's process identification");
	printf(" number  is : %X",getpid());
	getch();
}

Output :

Program's process identification number (PID) number is : 8E01_

stdio.h (Standard Input/Output Header File):

stdio.h refers to standard input/output header file. it is header file in C's standard library which contains constants, macros definitions and declarations of functions. It includes types used for various standard input and output operations.

The functions which are declared in stdio.h are very popular.

Member Functions :

Some of the standard member functions of stdio.h header files are,

Function Name	Description
scanf -	used to take input from the standard input stream
gets -	read characters from standard input while a new line is inserted
printf -	prints to the standard output stream
putc -	writes and returns a character to a stream
putchar -	It works as same of putc(stdout)
puts -	outputs a character string to stdout
fopen -	Opens a file to read or write
fwrite -	writes data to a file
fputs -	writes a string to a file
fread -	reads data from a file
fseek -	seeks file
fclose -	Closes a file
remove -	deletes or removes a file
rename -	renames a file
rewind -	adjusts the specified file so that the next I/O operation will take place at the beginning of the file. "rewind" is equivalent to fseek(f,0L,SEEK_SET);

Program :

/*  Program to demonstrate stdio.h header file working */

#include <stdio.h>
#include <conio.h>
void main()
{
	int no;
	clrscr();
	printf("\n\t Enter any number : ");
	scanf("%d",&no); // scanf()
	printf("\n\n\t Number is : %d",no); // printf()
	getch();
}

Output :

	Enter any number : 122

	Number is : 122_

stdlib.h (Standard Library header file):

'stdlib' is an acronym for Standard Library. It is header file of standard library in C which contains the functions like allocation of memory, conversions, process controls and other utilities.

Some of the standard member functions of stdlib.h header files are,

Function Name	Description
abs -	It returns the absolute value of a number.
atof -	It converts string into double value.
atoi -	It converts string into integer value.
atol -	It converts string into long integer value.
abort -	It terminates execution as abnormally.
exit -	It terminates execution of a program.
malloc -	It allocates memory from heap.
realloc -	It reallocates the memory.
calloc -	It allocates specific memory to array of object of sizes.
free -	Releases the memory.
rand -	It creates the series of pseudo numbers.
qsort -	It sorts an array.

Program :

/*  Program to demonstrate stdlib.h header file working */

#include <stdio.h>
#include <conio.h>
#include <stdlib.h>
void main()
{
	char no[10];
	clrscr();
	printf("\n\t Using abs(-194): %d",abs(-194)); // 1
	printf("\n\n\t Enter any number : ");
	scanf("%s",no);
	printf("\n\t Using atof() : %lf",atof(no)); // 2
	printf("\n\n\t Using atoi() : %d",atoi(no)); // 3
	getch();
}

Output :

	Using abs(-194) : 194

	Enter any number : 12

	Using atof() : 12.000000

	Using atoi() : 12_

string.h header file :

Some of the standard member functions of string.h header files are,

Function Name	Description
strlen -	Returns the length of a string.
strlwr -	Returns upper case letter to lower case.
strupr -	Returns lower case letter to upper case.
strcat -	Concatenates two string.
strcmp -	Compares two strings.
strrev -	Returns length of a string.
strcpy -	Copies a string from source to destination.

Program :

/*  Program to demonstrate string.h header file working */

#include <stdio.h>
#include <conio.h>
#include <string.h>
void main()
{
	char str[50];
	clrscr();
	printf("\n\t Enter your name : ");
	gets(str);
	printf("\nLower case of string: %s",strlwr(str));
	printf("\nUpper case of string: %s",strupr(str));
	printf("\nReverse of string: %s",strrev(str));
	printf("\nLength of String: %d",strlen(str));
	getch();
}

Output :

	Enter your name : Technoexam
Lower case of string: technoexam
Upper case of string: TECHNOEXAM
Reverse of string: MAXEONHCET	
Length of String: 10_

time.h header file :

The header file as 'time.h' is used to declare date and time functions which are primarily used to access date/time for manipulations.

Some of the standard member functions of time.h header files are,

Function Name	Description
asctime -	Returns string : day month date hours:min:sec year
clock -	Returns time if exists otherwise -1.
ctime -	Returns current time.
difftime -	Returns the difference in seconds between two times.
gmtime -	Returns the Greenwich Mean Time (GMT) / UTC.
localtime -	It returns local time.

Program :

/*  Program to demonstrate time.h header file working */

#include <stdio.h>
#include <conio.h>
#include <time.h>
void main()
{
	struct tm, *lcl;
	time_t t1;
	clrscr();
	t1 = time(NULL);
	lcl = localtime(&t1);
	printf("\n\tLocal Date and Time: %s",asctime(lcl));
	lcl = gmtime(&t1);
	printf("\n\n\tUTC Date and Time: %s",asctime(lcl));
	getch();
}

Output :

	Local Date and Time : Sat Nov 06 14:36:27 2010

	UTC Date and Time : Sat Nov 06 19:36:27 2010_

graphics.h header file :

The 'graphics.h' header file is used to declare graphics functions. It declares prototypes for the graphics functions.

Some of the standard member functions of graphics.h header files are,

Function Name	Description
initgraph -	Used to initialize graphics and load graphics driver.
line -	Used to draw a line as line(x1,y1,x2,y2).
bar -	Used to draw rectangle with diagonal, bar(x1,y1,x2,y2).
circle -	Used to draw circle, circle(x1,y1,radius).
cleardevice -	It clears the graphics screen.
closegraph -	Closes or shut downs graphics system.
rectangle -	Used to draw a rectangle.
setcolor -	It sets the current drawing color.
getcolor -	It returns the current drawing color.
floodfill -	Used to flood-fill bounded region.
settextstyle -	It sets current text features.
ellipse -	It draws ellipse, as ellipse(x,y,start,end,xrad,yrad).

Program :

/*  Program to demonstrate graphics.h header file working */

#include <stdio.h>
#include <conio.h>
#include <graphics.h>
void main()
{
	int gdriver=DETECT, gmode;
	clrscr();
	initgraph(&gdriver,&gmode,"c:\\tc\\bgi");
	circle(70,70,20);
	getch();
	closegraph();
}

Output :

Programs Library :

This section contains following various c programs which helps to build strong programming skills.

TCH01.C : Simple C Program
TCH02.C : Program to print value of existing number
TCH03.C : Program to demonstrate scanf() and printf()
Using Operators
Pyramid Patterns (14)
Matrix Operations (10)

Simple C Program : TCH01.C :

Program :

/*  Simple C Program  */

#include <stdio.h>
#include <conio.h>
void main()
{
	clrscr();
	printf("\n My first program in C !");
	getch();
}

Output :

My first program in C !_

Program to print value of existing number : TCH02.C :

Program :

/*  Program to print value of existing number  */

#include <stdio.h>
#include <conio.h>
void main()
{
	int no = 19;
	clrscr();
	printf("\n Number is : %d",no);
	getch();
}

Output :

Number is : 19 !_

Program to demonstrate scanf() and printf() : TCH03.C :

Program : */

#include <stdio.h>
#include <conio.h>
void main()
{
	int no;
	clrscr();
	printf("\n Enter any number :");
	scanf("%d",&no);
	printf("\n Number is : %d",no);
	getch();
}

Output :

Enter any number :12

Number is : 12_

Using Operators :

1. Program to calculate addition of two numbers (+)

Program to calculate addition of two numbers :

Program :

/*  Program to calculate addition of two numbers */

#include <stdio.h>
#include <conio.h>
void main()
{
	int a,b,c;
	clrscr();
	printf("\n Enter any 2 numbers : ");
	scanf("%d %d",&a,&b);
	c = a + b;
	printf("\n Addition is : %d",c);
	getch();
}

Output :

 Enter any 2 numbers : 12 14

 Addition is : 26_

2. Program to calculate subtraction of two numbers (-)

Program to calculate subtraction of two numbers :

Program :

/*  Program to calculate subtraction of two numbers */

#include <stdio.h>
#include <conio.h>
void main()
{
	int a,b,c;
	clrscr();
	printf("\n Enter any 2 numbers : ");
	scanf("%d %d",&a,&b);
	c = a - b;
	printf("\n Subtraction is : %d",c);
	getch();
}

Output :

 Enter any 2 numbers : 8 6

 Subtraction is : 2_

3. Program to calculate division of two numbers (/)

Program to calculate division of two numbers :

Program :

/*  Program to calculate division of two numbers */

#include <stdio.h>
#include <conio.h>
void main()
{
	int a,b,c;
	clrscr();
	printf("\n Enter any 2 numbers : ");
	scanf("%d %d",&a,&b);
	c = a / b;
	printf("\n Division is : %d",c);
	getch();
}

Output :

 Enter any 2 numbers : 12 5

 Division is : 2_

4. Program to calculate multiplication of two numbers (*)

Program to calculate multiplication of two numbers :

Program :

/*  Program to calculate multiplication of two numbers */

#include <stdio.h>
#include <conio.h>
void main()
{
	int a,b,c;
	clrscr();
	printf("\n Enter any 2 numbers : ");
	scanf("%d %d",&a,&b);
	c = a * b;
	printf("\n Multiplication is : %d",c);
	getch();
}

Output :

 Enter any 2 numbers : 8 12

 Multiplication is : 96_

5. Program to calculate modulus of two numbers (%)

Program to calculate modulus of two numbers :

Program :

/*  Program to calculate modulus of two numbers */

#include <stdio.h>
#include <conio.h>
void main()
{
	int a,b,c;
	clrscr();
	printf("\n Enter any 2 numbers : ");
	scanf("%d %d",&a,&b);
	c = a % b;
	printf("\n Modulus is : %d",c);
	getch();
}

Output :

 Enter any 2 numbers : 11 5

 Modulus is : 1_

C Programming Examples

Search an Array

/* This program accepts an array of N elements and a key. *
* Then it searches for the desired element. If the search *
* is successful, it displays "SUCCESSFUL SEARCH". *
* Otherwise, a message "UNSUCCESSFUL SEARCH" is displayed. */

#include <stdio.h>
void main()
{
int table[20];
int i, low, mid, high, key, size;

printf("Enter the size of an array\n");
scanf("%d", &size);

                 printf("Enter the array elements\n");
                 for(i = 0; i < size; i++)
                 {
                      scanf("%d", &table[i]);
                 }

printf("Enter the key\n");
scanf("%d", &key);

/* search begins */

low = 0;
high = (size - 1);

                 while(low <= high)
                 {
                      mid = (low + high)/2;
                      if(key == table[mid])
                      {
                            printf("SUCCESSFUL SEARCH\n");
                            return;
                      }
                      if(key < table[mid])
                            high = mid - 1;
                      else
                            low = mid + 1;
                 }

printf("UNSUCCESSFUL SEARCH\n");
} /* End of main() */
/*----------------------------------
Output
Output
Enter the size of an array
5
Enter the array elements
12
36
45
78
99
Enter the key
45
SUCCESSFUL SEARCH
----------------------------------*/

Accept an array of 10 elements and swap 3rd element with 4th using pointers

/* Write a C program to accept an array of 10 elements and swap 3rd *
* element with 4th element using pointers. And display the results */

#include <stdio.h>

void main()
{

float x[10];
int i,n;

void swap34(float *ptr1, float *ptr2 ); /* Function Declaration */

printf("How many Elements...\n");

scanf("%d", &n);

printf("Enter Elements one by one\n");

      for(i=0;i<n;i++)
      {
           scanf("%f",x+i);
      }

swap34(x+2, x+3); /* Function call:Interchanging 3rd element by 4th */

      printf("\nResultant Array...\n");
      for(i=0;i<n;i++)
      {
           printf("X[%d] = %f\n",i,x[i]);
      }
}     /* End of main() */

/* Function to swap the 3rd element with the 4th element in the array */

void swap34(float *ptr1, float *ptr2 ) /* Function Definition */
{
float temp;

      temp   = *ptr1;
      *ptr1 = *ptr2;
      *ptr2 = temp;
}                                            /* End of Function */

/*-------------------------------------------
Output
How many Elements...
10
Enter Elements one by one
10
20
30
40
50
60
70
80
90
100

Resultant Array...
X[0] = 10.000000
X[1] = 20.000000
X[2] = 40.000000
X[3] = 30.000000
X[4] = 50.000000
X[5] = 60.000000
X[6] = 70.000000
X[7] = 80.000000
X[8] = 90.000000
X[9] = 100.000000
----------------------------------------------------*/

Find the sum of two one-dimensional arrays using Dynamic Memory Allocation

/* Write a C program to find the sum of two one-dimensional arrays using *
* Dynamic Memory Allocation */

#include <stdio.h>
#include <alloc.h>
#include <stdlib.h>

void main()
{
int i,n;
int *a,*b,*c;

printf("How many Elements in each array...\n");
scanf("%d", &n);

      a = (int *) malloc(n*sizeof(int));
      b = (int *) malloc(n*sizeof(int));
      c =( int *) malloc(n*sizeof(int));

      printf("Enter Elements of First List\n");
      for(i=0;i<n;i++)
      {
           scanf("%d",a+i);
      }

      printf("Enter Elements of Second List\n");
      for(i=0;i<n;i++)
      {
           scanf("%d",b+i);
      }

      for(i=0;i<n;i++)
      {
           *(c+i) = *(a+i) + *(b+i);
      }

      printf("Resultant List is\n");
      for(i=0;i<n;i++)
      {
           printf("%d\n",*(c+i));
      }

} /* End of main() */

/*---------------------------------------
Output
How many Elements in each array...
4
Enter Elements of First List
1
2
3
4
Enter Elements of Second List
6
7
8
9
Resultant List is
7
9
11
13

----------------------------------------*/

Find the sum of all elements of an array using pointersas arguments

/* Write a C program to find the sum of all elements of *
* an array using pointersas arguments */

#include <stdio.h>

void main()
{
static int array[5]={ 200,400,600,800,1000 };
int sum;

int addnum(int *ptr); /* function prototype */

sum = addnum(array);

printf("Sum of all array elements = %5d\n", sum);

} /* End of main() */

int addnum(int *ptr)
{
int index, total=0;

      for(index = 0; index < 5; index++)
      {
           total += *(ptr+index);
      }
      return(total);
}
/*-----------------------------------
Output
Sum of all array elements = 3000
------------------------------------*/

Check if two numbers are equal

/* Write a C program to accept two integers and check if they are equal */

#include <stdio.h>
void main()
{
int m,n;

printf("Enter the values for M and N\n");
scanf("%d %d", &m,&n);

      if(m == n )
           printf("M and N are equal\n");
      else
           printf("M and N are not equal\n");

} /* End of main() */

/*------------------------------------
output
Enter the values for M and N
34 45
M and N are not equal

-------------------------------------*/

C Program to accept two matrices and check if they are equal

/* Write a C Program to accept two matrices and check if they are equal */

#include <stdio.h>
#include <conio.h>
#include <stdlib.h>

void main()
{
int A[10][10], B[10][10];
int i, j, R1, C1, R2, C2, flag =1;

printf("Enter the order of the matrix A\n");
scanf("%d %d", &R1, &C1);

printf("Enter the order of the matrix B\n");
scanf("%d %d", &R2,&C2);

   printf("Enter the elements of matrix A\n");
   for(i=0; i<R1; i++)
   {
     for(j=0; j<C1; j++)
     {
      scanf("%d",&A[i][j]);
     }
   }

   printf("Enter the elements of matrix B\n");
   for(i=0; i<R2; i++)
   {
     for(j=0; j<C2; j++)
     {
      scanf("%d",&B[i][j]);
     }
   }

   printf("MATRIX A is\n");
   for(i=0; i<R1; i++)
   {
     for(j=0; j<C1; j++)
     {
      printf("%3d",A[i][j]);
     }
     printf("\n");
   }

   printf("MATRIX B is\n");
   for(i=0; i<R2; i++)
   {
     for(j=0; j<C2; j++)
     {
      printf("%3d",B[i][j]);
     }
     printf("\n");
   }

/* Comparing two matrices for equality */

   if(R1 == R2 && C1 == C2)
   {
    printf("Matrices can be compared\n");
    for(i=0; i<R1; i++)
    {
           for(j=0; j<C2; j++)
           {
                 if(A[i][j] != B[i][j])
                 {
                       flag = 0;
                       break;
                 }
           }
      }
    }
    else
    { printf(" Cannot be compared\n");
       exit(1);
    }

    if(flag == 1 )
      printf("Two matrices are equal\n");
    else
      printf("But,two matrices are not equal\n");

}

/*------------------------------------------------------
Output
Enter the order of the matrix A
2 2
Enter the order of the matrix B
2 2
Enter the elements of matrix A
1 2
3 4
Enter the elements of matrix B
1 2
3 4
MATRIX A is
1 2
3 4
MATRIX B is
1 2
3 4
Matrices can be compared
Two matrices are equal
-------------------------------------------------------*/

Find the length of a string

/* Write a c program to find the length of a string *
* without using the built-in function */

#include <stdio.h>

void main()
{
char string[50];
int i, length = 0;

printf("Enter a string\n");
gets(string);

      for (i=0; string[i] != '\0'; i++) /*keep going through each */
      {                                 /*character of the string */
          length++;                     /*till its end */
      }
      printf("The length of a string is the number of characters in it\n");
      printf("So, the length of %s =%d\n", string, length);
}

/*----------------------------------------------------
Output
Enter a string
hello
The length of a string is the number of characters in it
So, the length of hello = 5

RUN2
Enter a string
E-Commerce is hot now
The length of a string is the number of characters in it
So, the length of E-Commerce is hot now =21
----------------------------------------------------------*/

Accept two strings and compare them

/* Program to accepts two strings and compare them. Finally it prints *
* whether both are equal, or first string is greater than the second *
* or the first string is less than the second string */

#include<stdio.h>
#include<conio.h>

void main()
{
int count1=0,count2=0,flag=0,i;
char str1[10],str2[10];

      clrscr();
      puts("Enter a string:");
      gets(str1);

      puts("Enter another string:");
      gets(str2);
      /*Count the number of characters in str1*/
      while (str1[count1]!='\0')
           count1++;
      /*Count the number of characters in str2*/
      while (str2[count2]!='\0')
           count2++;
      i=0;

      /*The string comparison starts with thh first character in each string and
      continues with subsequent characters until the corresponding characters
      differ or until the end of the strings is reached.*/

      while ( (i < count1) && (i < count2))
      {
           if (str1[i] == str2[i])
           {
                 i++;
                 continue;
           }
           if (str1[i]<str2[i])
           {
                 flag = -1;
                 break;
           }
           if (str1[i] > str2[i])
           {
                 flag = 1;
                 break;
           }
      }

      if (flag==0)
          printf("Both strings are equal\n");
      if (flag==1)
          printf("String1 is greater than string2\n", str1, str2);
      if (flag == -1)
          printf("String1 is less than string2\n", str1, str2);
      getch();
}
/*----------------------------------------
Output
Enter a string:
happy
Enter another string:
HAPPY
String1 is greater than string2

RUN2
Enter a string:
Hello
Enter another string:
Hello
Both strings are equal

RUN3
Enter a string:
gold
Enter another string:
silver
String1 is less than string2
----------------------------------------*/

Convert number of days to number of years, weeks and days

/*    Write a c program to convert given number of days to a measure of time
*    given in years, weeks and days. For example 375 days is equal to 1 year
*    1 week and 3 days (ignore leap year)
*/

#include <stdio.h>
#define DAYSINWEEK 7

void main()
{
int ndays, year, week, days;

printf("Enter the number of days\n");
scanf("%d",&ndays);

    year = ndays/365;
    week = (ndays % 365)/DAYSINWEEK;
    days = (ndays%365) % DAYSINWEEK;

printf ("%d is equivalent to %d years, %d weeks and %d days\n",
ndays, year, week, days);
}

/*-----------------------------------------------
Output
Enter the number of days
375
375 is equivalent to 1 years, 1 weeks and 3 days

Enter the number of dayy
423
423 is equivalent tt 1 years, 8 weeks and 2 days

Enter the number of days
1497
1497 is equivalent to 4 years, 5 weeks and 2 days
---------------------------------------------------*/

Find GCD and LCM of two integers

/* Write a C program to find the GCD and LCM of two integers *
* output the results along with the given integers. Use Euclids' algorithm*/

#include <stdio.h>
#include <conio.h>

void main()
{
int num1, num2, gcd, lcm, remainder, numerator, denominator;
clrscr();

printf("Enter two numbers\n");
scanf("%d %d", &num1,&num2);

if (num1 > num2)
    {
       numerator = num1;
       denominator = num2;
    }
    else
    {
       numerator = num2;
       denominator = num1;
    }
    remainder = num1 % num2;
    while(remainder !=0)
    {
         numerator   = denominator;
         denominator = remainder;
         remainder   = numerator % denominator;
    }
    gcd = denominator;
    lcm = num1 * num2 / gcd;
    printf("GCD of %d and %d = %d \n", num1,num2,gcd);
    printf("LCM of %d and %d = %d \n", num1,num2,lcm);
}                /* End of main() */
/*------------------------
Output
RUN 1
Enter two numbers
5
15
GCD of 5 and 15 = 5
LCM of 5 and 15 = 15
------------------------------*/

Find the sum of odd numbers and sum of even numbers from 1 to N

/* Write a C program to find the sum of odd numbers and *
* sum of even numbers from 1 to N. Output the computed *
* sums on two different lines with suitable headings */

#include <stdio.h>
#include <conio.h>

void main()
{
int i, N, oddSum = 0, evenSum = 0;

clrscr();

printf("Enter the value of N\n");
scanf ("%d", &N);

for (i=1; i <=N; i++)
       {
                 if (i % 2 == 0)
                          evenSum = evenSum + i;
                 else
                          oddSum = oddSum + i;
         }

printf ("Sum of all odd numbers = %d\n", oddSum);
printf ("Sum of all even numbers = %d\n", evenSum);
}
/*-----------------------------
Output
RUN1

Enter the value of N
10
Sum of all odd numbers = 25
Sum of all even numbers = 30

RUN2
Enter the value of N
50
Sum of all odd numbers = 625
Sum of all even numbers = 650

------------------------------*/

Simulate a simple calculator to perform arithmetic operations on integers

/* Write a C program to simulate a simple calculator to perform *
* arithmetic operations like addition, subtraction,multiplication *
* and division only on integers. Error message should be repoetrd *
* if any attempt is made to divide by zero */

#include <stdio.h>
#include <conio.h>

void main()
{
char oper; /* oper is an operator to be selected */
float n1, n2, result;

clrscr();

printf ("Simulation of a Simple Calculator\n\n");

printf("Enter two numbers\n");
scanf ("%f %f", &n1, &n2);

fflush (stdin);

printf("Enter the operator [+,-,*,/]\n");
scanf ("%c", &oper);

         switch (oper)
         {
                 case '+': result = n1 + n2;
                          break;
                 case '-': result = n1 - n2;
                          break;
                 case '*': result = n1 * n2;
                          break;
                 case '/': result = n1 / n2;
                          break;
                 default : printf ("Error in operation\n");
                          break;
         }

printf ("\n%5.2f %c %5.2f= %5.2f\n", n1,oper, n2, result);

}
/*-----------------------------
Output
Simulation of Simple Calculator

Enter two numbers
3 5
Enter the operator [+,-,*,/]
+

3.00 + 5.00= 8.00

RUN2
Simulation of Simple Calculator

Enter two numbers
12.75
8.45
Enter the operator [+,-,*,/]
-

12.75 - 8.45= 4.30

RUN3
Simulation of Simple Calculator

Enter two numbers
12 12
Enter the operator [+,-,*,/]
*

12.00 * 12.00= 144.00

RUN4
Simulation of Simple Calculator

Enter two numbers
5
9
Enter the operator [+,-,*,/]
/

5.00 / 9.00= 0.56

------------------------------*/

Check whether a given integer number is positive or negative

/* Write a C program to check whether a given integer *
* number is positive or negative*/

#include <stdio.h>
#include <conio.h>

void main()
{
int number;
clrscr();

printf("Enter a number\n");
scanf ("%d", &number);

      if (number > 0)
           printf ("%d, is a positive number\n", number);
      else
           printf ("%d, is a negative number\n", number);

}
/*-----------------------------
Output
Enter a number
-5
-5, is a negative number

RUN2
Enter a number
89
89, is a positive number
------------------------------*/

Check whether a given integer is odd or even

/* Write a C program to check whether a given integer is odd or even*/

#include <stdio.h>
#include <conio.h>

void main()
{
int ival, remainder;

clrscr();

printf("Enter an integer :");
scanf ("%d", &ival);

remainder = ival % 2;

   if (remainder == 0)
      printf ("%d, is an even integer\n", ival);
   else
      printf ("%d, is an odd integer\n", ival);

}
/*-----------------------------
Output

RUN1

Enter an integer :13
13, is an odd integer

RUN2
Enter an integer :24
24, is an even integer

---------------------------------*/

Find the area of a circle, given the radius

/* Write a C program to find the area of a circle, given the radius*/

#include <stdio.h>
#include <conio.h>
#include <math.h>
#define PI 3.142

void main()
{
float radius, area;
clrscr();

printf("Enter the radius of a circle\n");
scanf ("%f", &radius);

area = PI * pow (radius,2);

printf ("Area of a circle = %5.2f\n", area);
}

/*-----------------------------
Output

RUN1
Enter the radius of a circle
3.2
Area of a circle = 32.17

RUN 2
Enter the radius of a circle
6
Area of a circle = 113.11

------------------------------*/

Find the area of a triangle, given three sides

/* Write a C program to find the area of a triangle, given three sides*/

#include <stdio.h>

#include <conio.h>

#include <math.h>

void main()

{

int s, a, b, c, area;

clrscr();

printf("Enter the values of a,b and c\n");

scanf ("%d %d %d", &a, &b, &c);

/* compute s*/

s = (a + b + c) / 2;

area = sqrt ( s * (s-a) * (s-b) * (s-c));

printf ("Area of a triangale = %d\n", area);

}

/*-----------------------------

Output

Enter the values of a,b and c

Area of a triangale = 6

------------------------------*/

Define, Initialize, Read and Write a Structure

/* structure define , initial , read & right program */

#include<stdio.h>

#include<conio.h>

struct st // Structure declaration

{

int rl;

char nm[15];

};

void main()

{

struct st s; // object create

struct st s2={2000, "hansraj"}; // object create and initialization

clrscr();

// first student record read from keyboard

printf("enter roll number & name\n");

scanf("%d%s", &s.rl,s.nm);

printf("Your first Student Data\n");

printf("rl no.=%d\n",s.rl);

printf("nm =%s\n",s.nm);

printf("Your II Student Data\n");

printf("rl no.=%d\n",s2.rl);

printf("nm =%s\n",s2.nm);

getch();

}

Define, Initialize, Read and Write a nested Structure

/* structure define , initial , read & right program */

#include<stdio.h>

#include<conio.h>

struct date

{

int dd;

int mm;

int yy;

};

struct st // nested Structure(structure within structure) declaration

{

int rl;

char nm[15];

struct date dob; // dob is date object

};

void main()

{

struct st s; // object create

struct st s2={2000, "hansraj", 15, 10 ,1070 }; // object create and initialization

clrscr();

// first student record read from keyboard

printf("enter roll number & name\n");

scanf("%d%s", &s.rl,s.nm);

printf("enter date of birth \n");

scanf("%d%d%d", &s.dob.dd,&s.dob.mm,&s.dob.yy);

printf("Your first Student Data\n");

printf("rl no.=%d\n",s.rl);

printf("nm =%s\n",s.nm);

printf("Date of birth - %d-%d-%d\n", s.dob.dd,s.dob.mm, s.dob.yy);

printf("Your II Student Data\n");

printf("rl no.=%d\n",s2.rl);

printf("nm =%s\n",s2.nm);

printf("Date of birth - %d-%d-%d\n", s2.dob.dd,s2.dob.mm, s2.dob.yy);

getch();

}

Define Structure of Array

/* structure of array */

/* Nested Structure */

#include<stdio.h>

#include<conio.h>

struct date

{

int dd;

int mm;

int yy;

};

struct st // nested Structure(structure within structure) declaration

{

int rl;

char nm[15];

struct date dob; // dob is date object

};

void main()

{

struct st s[100];

int i,n;

clrscr();

printf("How many student -> ");

scanf("%d", &n);

for(i=0;i<n;i++)

{

printf("enter roll number , name and date of birth of %d student \n",i+1);

scanf("%d%s%d%d%d", &s[i].rl,s[i].nm, &s[i].dob.dd,&s[i].dob.mm,&s[i].dob.yy);

}

printf("Your Student Data\n");

for(i=0;i<n;i++)

{

printf("%10d\t%-20s\t%2d-%2d-%4d\n",s[i].rl,s[i].nm,s[i].dob.dd,s[i].dob.mm, s[i].dob.yy);

}

getch();

}

Calculating total and percentage marks of a student using structure

#include<stdio.h>

#include<conio.h>

struct student

{

int rl;

char nm[20];

int m1;

int m2;

int m3;

int t;

float per;

};

void main()

{

struct student a;

clrscr();

printf(" Enter RollNo, Name amd three sub marks\n");

scanf("%d%s%d%d%d",&a.rl,&a.nm,&a.m1,&a.m2,&a.m3);

a.t=a.m1+a.m2+a.m3;

a.per=a.t/3.0;

printf("rollno=%d\n",a.rl);

printf("Name=%sk\n",a.nm);

printf("m1=%d\n",a.m1);

printf("m2=%d\n",a.m2);

printf("m3=%d\n",a.m3);

printf("total=%d\n",a.t);

printf("per=%f\n",a.per);

getch();

}

Using Structure within Structure in a Program

/* STRUCTURE WITHIN STRUCTURE PROGRAMM */

#include<stdio.h>

#include<conio.h>

struct inv

{

char inm[15];

int qty;

int rate;

int amt;

struct date

{

int dd;

int mm;

int yy;

}d;

}

list[100];

void main()

{

int i,n;

clrscr();

printf("Enter the Total no of items\n");

scanf("%d",&n);

printf("Enter the item name, qty and rate,date\n");

for(i=0;i<n;i++)

{

scanf("%s%d%d%d%d%d", list[i].inm,&list[i].qty,&list[i].rate,

&list[i].d.dd,&list[i].d.mm, &list[i].d.yy);

list[i].amt = list[i].qty*list[i].rate;

}

printf("ITEM NAME QTY RATE AMT date\n");

for(i=0;i<n;i++)

printf("%-15s%5d%5d%7d %d-%d-%d\n",list[i].inm,list[i].qty,list[i].rate,

list[i].amt,list[i].d.dd,list[i].d.mm,list[i].d.yy );

getch();

}

Sort a string array in ascending order

//Write a C program to sort a string array in ascending order.

#include<stdio.h>

#include<conio.h>

#include<string.h>

void main()

{

char st[20],ch;

int i,j,l;

clrscr();

printf("enter any string:");

gets(st);

l=strlen(st);

/* sorting process */

for(i=1;i<l;i++)

for(j=0;j<l-i;j++)

if(st[j]>st[j+1])

{

ch=st[j];

st[j] = st[j+1];

st[j+1]=ch;

}

printf("Sorted string is \n");

printf("%s\n",st);

getch();

}

Check whether the given String is Palindrome or not

//Write a C program to check whether the given String Palindrom or not .

#include<stdio.h>

#include<conio.h>

#include<string.h>

void main()

{

char st[20];

int flag=0,i,l;

clrscr();

printf("enter any string\n");

gets(st);

l=strlen(st);

for(i=0;i<l/2;i++)

if(st[i]!=st[l-1-i])

{

flag=1;

break;

}

if(flag==0)

printf("String is Palindrom");

else

printf("String is not palindrom\n");

getch();

}

Print a String in Reverse Order

/* read any string print it reverse order */

#include<stdio.h >

#include<conio.h>

#include<string.h>

void main()

{

char st[20],ch;

int i,l;

clrscr();

printf("Enter the string :-> ");

gets(st);

l=strlen(st);

printf("Original String :-> %s\n",st);

/* Reverse String Logic */

for(i=0;i<l/2;i++)

{

ch=st[i];

st[i]= st[l-1-i];

st[l-1-i]=ch;

}

printf("Reverse String is :-> %s\n",st);

getch();

}

Replacing a word in a text

#include <stdio.h>

#include <string.h>

#include<conio.h>

void main()

{

char text[100],word[10],rpwrd[10],str[10][10];

int i=0,j=0,k=0,w,p;

clrscr();

printf("PLEASE WRITE ANY TEXT.\n");

printf("GIVE ONLY ONE SPACE AFTER EVERY WORD\n");

printf("WHEN COMPLETE PRESS Ctrl-Z \n");

gets(text);

printf("\nENTER WHICH WORD IS TO BE REPLACED\n");

scanf("%s",word);

printf("\nENTER BY WHICH WORD THE %s IS TO BE REPLACED\n",word);

scanf("%s",rpwrd);

p=strlen(text);

for (k=0; k<p; k++)

{

if (text[k]!=' ')

{

str[i][j] = text[k];

j++;

}

else

{

str[i][j]='\0';

j=0; i++;

}

str[i][j]='\0';

w=i;

for (i=0; i<=w; i++)

{

if(strcmp(str[i],word)==0)

strcpy(str[i],rpwrd);

printf("%s ",str[i]);

}

getch();

}

Display Strings in alphabetical order

/** PROGRAM Read n values (string) from keyboard

display string list in alphabetical order ****/

#include<conio.h>

#include<stdio.h>

#include<string.h>

main()

{

int i,j,n;

char s[20][20],t[20];

clrscr();

printf("HOW MANY COUNTRY\n");

scanf("%d",&n);

printf(" ENTER ANY %d COUNTRY NAME \n",n);

for(i=0;i<n;i++)

scanf("%s",s[i]);

for(i=0;i<n-1;i++)

for(j=i+1;j<n;j++)

if(strcmp(s[i],s[j])>0)

{

strcpy(t,s[i]);

strcpy(s[i],s[j]);

strcpy(s[j],t);

}

printf("\n THE ALPHABATICAL LIST IS \n");

for(i=0;i<n;i++)

printf("%s\n",s[i]);

getch();

}

Find Palindrome String

/** PROGRAM FOR PALINDROME STRING ****/

/* Calculate reverse string then match the original string */

#include<stdio.h>

#include<string.h>

#include<conio.h>

main()

{

int i,j,c,x;

char s1[20],s2[20];

clrscr();

printf("INPUT IS : \n");

printf(" ENTER ANY STRING \n");

scanf("%s",s1);

x = strlen(s1);

printf("OUT PUT IS : \n\n");

j=0;

for(i=x-1;i>=0;i--)

{

printf("%c",s1[i]);

s2[j]=s1[i];

j++;

}

s2[j] = '\0';

printf("\n %s \n",s2);

if(strcmp(s1,s2)==0)

printf(" STRING IS PALLENDROM \n ");

else

printf("STRING IS NOT PALLENDROM \n");

getch();

}

Read a string and sort it in alphabetical order using bubble sort

/* program read any string and sort in alphabetical order

using bubble sort */

#include<stdio.h>

#include<conio.h>

#include<string.h>

void main()

{

char st[25],temp;

int l,i,j;

clrscr();

printf("enter Any Sting\n");

gets(st);

l=strlen(st);

/*Logic Bubble Sort */

for(i=1;i<l;i++)

for(j=0;j<l-i;j++)

if(st[j]>st[j+1])

{

temp=st[j];

st[j]=st[j+1];

st[j+1] =temp;

}

printf("sorted string \n");

printf("%s",st);

getch();

}

Sort an array using function

/* Read n value into array Sort array using function */

#include<stdio.h>

#include<conio.h>

void swap(int *, int *);

void read(int *,int);

void display(int *,int);

void sort(int *, int);

void main()

{

int n,a[100];

clrscr();

printf("Enter Total value of array :-");

scanf("%d",&n);

printf("enter %d value\n",n);

read(a,n);

printf("\nOriginal List:\n");

display(a,n);

sort(a,n);

printf("\nSorted list:\n");

display(a,n);

getch();

}

void swap(int *x, int *y)

{

int t;

t = *x;

*x = *y;

*y = t;

}

void read(int *p,int t)

{

int *i;

for(i=p;i<p+t;i++)

scanf("%d",i);

}

void display(int *p,int t)

{

int *i;

for(i=p;i<p+t;i++)

printf("%5d",*i);

printf("\n");

}

void sort(int *p, int t)

{

int *i,j;

for(j=1;j<t;j++)

for(i=p;i<p+t-j;i++)

if(*i >= *(i+1))

swap(i,i+1);

}

Swap two integer numbers using function with pointer call by reference

/* Program swap two integer number using function with pointer

call by reference */

#include<conio.h>

#include<stdio.h>

void main()

{

int a,b;

void swap(int *,int *);

printf("enter the value of a & b\n");

scanf("%d%d",&a,&b);

printf("Before Swapping \n");

printf("a = %d\nb=%d\n",a,b);

swap(&a,&b);

printf("After Swapping \n");

printf("a = %d\nb=%d\n",a,b);

getch();

}

void swap(int *x,int *y)

{

int t;

t=*x;

*x = *y;

*y = t;

}

Using Malloc Function

/* dynamic memory

read n value into arry using dynamic memory allocation

using malloc function */

#include<stdio.h>

#include<conio.h>

#include<stdlib.h>

void main()

{

int *p,n,*i;

clrscr();

printf("enter vhow many value stored :\n" );

scanf("%d",&n);

p=(int*)malloc(sizeof(int)*n);

printf("enter %d value \n",n);

for(i=p;i<p+n;i++)

scanf("%d",i);

printf("your data list is \n");

for(i=p;i<p+n;i++)

printf("%5d",*i);

getch();

}

Using Calloc Function

/* dynamic memory

read list value at run time

calloc is use to allocate the memory at run time

and free is used to delete unwanted memory */

#include<stdio.h>

#include<conio.h>

#include<stdlib.h>

void main()

{

int c=0,*p,n,*i;

clrscr();

printf("enter vhow many value stored :\n" );

scanf("%d",&n);

p=(int*)calloc(sizeof(int),n);

printf("enter %d value \n",n);

printf("If Terminate in between entered Negative value \n");

for(i=p;i<p+n;i++)

{

scanf("%d",i);

c++;

if(*i < 0) break;

}

free(p);

printf("your data list is \n");

for(i=p;i<p+c;i++)

printf("%5d",*i);

getch();

}

Find Prime Numbers Using Function

/*PROGRAM FOR PRIME NUMBER using FUNCTION **/

#include<stdio.h>

#include<conio.h>

#include<math.h>

void main()

{

int prime(int x);

int n,f;

clrscr();

printf(" ENTER THE ANY NUMBER \n");

scanf("%d",&n);

f=prime(n);

if(f==1)

printf(" NUMBER IS PRIME \n");

else

printf("NUMBER IS NOT PRIME \n");

getch();

}

int prime(int x)

{

int i,a,r=0;

a=sqrt(x);

if((x==1)||(x==2))

return(0);

else

{

for(i=2;i<=a;i++)

if(x%i==0)

return(0);

return(1);

}

Concatenate and Compare two Strings

//Write a C++ Program using for the follwing task:-

//(a) Concatenate two Strings

//(b) Comparision of Two strings

#include<iostream.h>

#include<conio.h>

#include<string.h>

class string

{

private:

char st1[15];

char st2[15];

char st[30];

public:

void read();

void concat();

void cmpr();

};

void string ::read()

{

cout<<"enter First String :"<<endl;

cin>>st1;

cout<<"enter Second String :"<<endl;

cin>>st2;

}

void string::concat()

{

strcpy(st,st1);

strcat(st," ");

strcat(st,st2);

cout<<"After concatenate :"<<st<<endl;

}

void string::cmpr()

{

if (strcmp(st1,st2)==0)

cout<<"Both String are Identical "<<endl;

else

cout<<"both String are different "<<endl;

}

void main()

{

string x;

clrscr();

x.read();

x.concat();

x.cmpr();

getch();

}

Calculate HCF of three integers

/*PROGRAM read two integer calculate hcf of three integer */

#include<stdio.h>

#include<conio.h>

#include<math.h>

void main()

{

int hcf(int x,int y);

int a,b,c,h;

clrscr();

printf(" ENTER THE integer \n");

scanf("%d%d%d",&a,&b,&c);

h=hcf(hcf(a,b),c);

printf("HCF = %d\n",h);

getch();

}

int hcf(int x,int y)

{

while(x!=y)

if(x>y) x=x-y;

else y=y-x;

}

C Programming Recursion

A function that calls itself is known as recursive function and the process of calling function itself is known as recursion in C programming.

Example of recursion in C programming

Write a C program to find sum of first n natural numbers using recursion. Note: Positive integers are known as natural number i.e. 1, 2, 3....n

#include <stdio.h>

int sum(int n);

int main(){

    int num,add;

    printf("Enter a positive integer:\n");

    scanf("%d",&num);

    add=sum(num);

    printf("sum=%d",add);

int sum(int n){

    if(n==0)

       return n;

    else

       return n+sum(n-1);    /*self call  to function sum() */

Output

Enter a positive integer:

In, this simple C program, sum() function is invoked from the same function. If n is not equal to 0 then, the function calls itself passing argument 1 less than the previous argument it was called with. Suppose, n is 5 initially. Then, during next function calls, 4 is passed to function and the value of argument decreases by 1 in each recursive call. When, n becomes equal to 0, the value of n is returned which is the sum numbers from 5 to 1.

For better visualization of recursion in this example:

sum(5)

=5+sum(4)

=5+4+sum(3)

=5+4+3+sum(2)

=5+4+3+2+sum(1)

=5+4+3+2+1+sum(0)

=5+4+3+2+1+0

=5+4+3+2+1

=5+4+3+3

=5+4+6

=5+10

=15

Every recursive function must be provided with a way to end the recursion. In this example when, n is equal to 0, there is no recursive call and recursion ends.

Advantages and Disadvantages of Recursion

Recursion is more elegant and requires few variables which make program clean. Recursion can be used to replace complex nesting code by dividing the problem into same problem of its sub-type.

In other hand, it is hard to think the logic of a recursive function. It is also difficult to debug the code containing recursion.

Sum of digit using Recursion

/* Recursive function sum of digit */

#include<conio.h>

#include<stdio.h>

void main()

{

int sumdigit(int x);

int n,sum;

printf ("Enter Integer number \n");

scanf("%d",&n);

sum=sumdigit(n);

printf ("Sum of Digit :-> %d\n", sum);

getch();

}

/* Function sum of digit define as recursive */

int sumdigit(int x)

{

int s=0,d;

if(x==0) return (0);

d= x%10;

s+=d+sumdigit(x/10);

return(s);

}

Fibonacci series Using Recursion

/* Fibonacci series Using Recursion */

#include<stdio.h>

#include<conio.h>

void main()

{

int fib(int ) ;

int i,r,n;

clrscr();

printf("Enter How Many terms to be print \n");

scanf("%d",&n);

printf("Fibonacci series is :\n");

for(i=1;i<=n;i++)

{

r=fib(i);// Calling with Argument

printf("%5d",r);

}

getch();

}

// Function defination

int fib(int x)

{

int f;

if (x==1)

return(0);

else if (x==2)

return(1);

else

f= fib(x-1)+fib(x-2);

return(f);

}

Factorial Function Using Recursion

/* Factorial Function Using Recursion */

#include<stdio.h>

#include<conio.h>

void main()

{

int fact(int ) ;

int r,n;

clrscr();

printf("Enter the Value of n\n");

scanf("%d",&n);

r=fact(n);// Calling with Argument

printf("Factorial value = %d\n",r);

getch();

}

/*define factorial function as recursive */

int fact (int x)

{

int f;

if (x==0||x==1)

return(1);

else

f = x*fact(x-1);

return(f);

}

Matrix Multiplication using function

/* Matrix Multiplication using function */

#include<stdio.h >

#include<conio.h>

int i,j,k;

void main()

{

int a[10][10],b[10][10],c[10][10],m,n,p,q;

void mul(int x[10][10],int y[10][10],int z[10][10],int m,int n,int p,int q);

void read(int x[10][10],int m,int n);

void display(int x[10][10], int m,int n);

clrscr();

printf("Enter the size of A Mtrix (Row and Col): \n");

scanf("%d%d",&m,&n);

printf("Enter the size of B Mtrix (Row and Col): \n");

scanf("%d%d",&p,&q);

if(n!=p)

{

printf("Multiplication Not Possible\n Please re-enter\n");

printf("correct size and try again .....\n");

}

else

{

read(a,m,n);

read(b,m,n);

mul(a,b,c,m,n,p,q);

printf("A Matrix is :\n");

display(a,m,n);

printf("B Matrix is :\n");

display(b,m,n);

printf("C Matrix is :\n");

display(c,m,n);

}

getch();

}

void mul(int x[10][10],int y[10][10],int z[10][10],int m,int n,int p,int q)

{

for (i=0;i<m;i++)

for(j=0;j<q;j++)

{

z[i][j]=0;

for(k=0;k<n;k++)

z[i][j]+= x[i][k]*y[k][j];

}

void read(int x[10][10], int m,int n)

{

printf("Enter Matrix Value Row by Row\n");

for (i=0;i<m;i++)

for(j=0;j<n;j++)

scanf("%d",&x[i][j]);

}

void display(int x[10][10], int m,int n)

{

for (i=0;i<m;i++)

{

for(j=0;j<n;j++)

printf("%5d",x[i][j]);

printf("\n");

}

printf("\n");

}

Find Length of Array using Function

/* in Function with array we use the array name and size of array

with calling function and pass these argument to the called function's

formal argument. Formal function argument should be array type and size

must be integer */

/* Program single d */

#include<stdio.h>

#include<conio.h>

int i,j;

void main()

{

int a[10][10],m;

auto int n;

void read(int x[10][10],int row, int col);

void display(int x[10][10],int row, int col);

clrscr();

printf("Enter the size of array \n");

scanf("%d%d",&m,&n);

read(a,m,n);

printf("your 2d array is :\n");

display(a,m,n);

getch();

}

void read(int x[10][10],int row, int col)

{

for( i=0;i<row;i++)

for(j=0;j<col;j++)

scanf("%d",&x[i][j]);

}

void display(int x[10][10],int row, int col)

{

for( i=0;i<row;i++)

{

for(j=0;j<col;j++)

printf("%5d",x[i][j]);

printf("\n");

}

Insertion and Quick Sort

#include <stdio.h>

#include <iostream.h>

#include <stdlib.h>

#include <values.h>

#include <time.h>

#include <string.h>

const int max=1000;

int list[max];

FILE *fp;

void insertion(int aa[],int max1)

{

int a,b,v;

for(a=1;a<max1;a++)

{

v = aa[a];

b = a;

while(aa[b-1] > v)

{

aa[b] = aa[b-1];

b = b - 1;

}

aa[b] = v;

}

void quicksort(int min1,int max2)

{

int t;

if (max2 > min1)

{

int v = list[max2];

int i = min1 - 1;

int j = max2;

{

i = i + 1;

} while (list[i] < v);

{

j = j - 1;

} while (list[j] > v);

int t = list[i];

list[i] = list[j];

list[j] = t;

} while (j > i);

list[j] = list[i];

list[i] = list[max2];

list[max2] = t;

quicksort(min1,i-1);

quicksort(i+1,max2);

}

void main()

{

int i,j,k,l;

char any1[8],any2[8];

cout << "Enter a file name\n";

cin >> any1;

/*if(strlen(any1) > 12)

cout << "File name input error."; */

fp = fopen(any1,"wb");

for(j=0;j<30000;j++)

{

k = rand();

fprintf(fp,"%d\n",k);

}

fclose(fp);

fp = fopen(any1,"rb");

i = 0;

while (fscanf(fp,"%d\n",l) != 0)

{

list[i] = l;

i = i + 1;

}

fclose(fp);

/*int min = 0;

quicksort(min,max); */

insertion(list,max);

cout << "Enter an output file : ";

cin >> any2;

fp = fopen(any2,"wb");

for(i=0;i<max;i++)

{

int r = list[i];

fwrite(&r,sizeof(int),1,fp);

}

fclose(fp);

}

Create and Sort a Heap

/* HPSORT.C : PROGRAM TO CREATE A HEAP AND TO SORT A HEAP, HEAP IS STORED IN AN ARRAY */

#include<stdio.h>

#include<conio.h>

void crheap(int [], int);

void processheap(int [],int);

int main(void)

{

int k[50],child,parent,q,key,n,t,i;

clrscr();

printf("\n enter the no. of elements: ");

scanf(" %d",&n);

printf("\n Now enter the array elements: ");

for(i=1;i<=n;i++)

scanf(" %d",&k[i]);

crheap(k,n);

processheap(k,n);

return(0);

}

/*function to create a heap, in this algorithm the value of a child

node is saved into a key and then if its parent has value less than the

key then the parent node is shifted to its child place and this process

of copying the parent node to its child's place continues until the

correct place of key is found or the root is reached, in that case key

is inserted at the root's place

function to create a heap, in this algorithm every time

a child node has value greater than its parent the two are interchanged */

void crheap(int k[],int n)

{

int i,q, parent,child,temp;

for(q=2;q<=n;q++)

{

child=q;

parent=(int)child/2;

while(child >1 && k[child] > k[parent])

{

temp=k[child];

k[child]= k[parent];

k[parent]=temp;

child=parent;

parent=(int)child/2;

if(parent < 1)

parent=1;

}

printf("\n Now the array in heap form is: ");

for(i=1;i<=n;i++)

printf(" %3d",k[i]);

}

/* function to sort a heap */

void processheap(int k[],int n)

{

int current,parent,child,i,maxnodes;

for(maxnodes=n;maxnodes>=2;maxnodes--)

{

current=k[maxnodes];;

k[maxnodes]=k[1];

/* adjust the array to be a heap of size n-1 */

parent=1;

/* obtain the larger of the root's children */

if (maxnodes-1 >= 3 && k[3] > k[2])

child=3;

else

child = 2;

/* move keys upwards to find place for current */

while (child<=maxnodes-1 && k[child]>=current)

{

k[parent]=k[child];

parent=child;

child=child*2;

if(child+1 <= maxnodes-1 && k[child+1] > k[child])

child = child + 1;

}

k[parent]=current;

} /* end of for */

printf("\n The sorted array is : ");

for(i=1;i<=n;i++)

printf("%4d",k[i]);

getch();

}

Create/Define a Tree

/* Program Tree define(Create ) and insert,print,depth */

#include <stdio.h>

#include <malloc.h>

#include <stdio.h>

#include <conio.h>

typedef struct TREE

{

int data;

struct TREE *left;

struct TREE *right;

} TREE;

int main()

{

int data,depth;

TREE *tree =NULL;

TREE *InsertTree(int data,TREE *p);

TREE *PrintTreeTriangle(TREE *tree, int level);

int TreeDepth(TREE *tree,int *depth,int level);

clrscr();

while(1)

{

printf("\nKey to insert|");

scanf("%d", &data);

if (data==0)

break;

tree =InsertTree(data,tree);

printf("\n Tree Display;\n");

PrintTreeTriangle(tree,1);

depth=0;

TreeDepth(tree,&depth,0);

printf("\nTree Depth =%d\n",depth);

}

return(0);

}

TREE *InsertTree(int data,TREE *p)

{

if(!p)

{

p=(TREE*)malloc(sizeof(TREE));

p->data=data;

p->left=NULL;

p->right=NULL;

return(p);

}

if(data < p->data)

p->left=InsertTree(data,p->left);

else

if(data > p->data)

p->right=InsertTree(data,p->right);

return(p);

}

TREE *PrintTreeTriangle(TREE *tree, int level)

{

int i;

if(tree)

{

PrintTreeTriangle(tree->right,level+1);

printf("\n\n");

for(i=0;i<level;i++)

printf(" ");

printf("%d",tree->data);

PrintTreeTriangle(tree->left,level+1);

}

return(NULL);

}

int TreeDepth(TREE *tree,int *depth,int level)

{

if(tree)

{

if (level>*depth)

*depth=level;

TreeDepth(tree->left,depth,level+1);

TreeDepth(tree->right,depth,level+1);

}

return(0);

}

Stack PUSH & POP Implementation using Arrays

/*STACK PUSH() AND POP() IMPLEMENTATION USING ARRAYS*/

#include <stdio.h>

#include<conio.h>

#define MAX 5

int top, status;

/*PUSH FUNCTION*/

void push (int stack[], int item)

{ if (top == (MAX-1))

status = 0;

else

{ status = 1;

++top;

stack [top] = item;

}

/*POP FUNCTION*/

int pop (int stack[])

{

int ret;

if (top == -1)

{ ret = 0;

status = 0;

}

else

{ status = 1;

ret = stack [top];

--top;

}

return ret;

}

/*FUNCTION TO DISPLAY STACK*/

void display (int stack[])

{ int i;

printf ("\nThe Stack is: ");

if (top == -1)

printf ("empty");

else

{ for (i=top; i>=0; --i)

printf ("\n--------\n|%3d |\n--------",stack[i]);

}

printf ("\n");

}

/*MAIN PROGRAM*/

void main()

{

int stack [MAX], item;

int ch;

clrscr ();

top = -1;

{ do

{ printf ("\NMAIN MENU");

printf ("\n1.PUSH (Insert) in the Stack");

printf ("\n2.POP (Delete) from the Stack");

printf ("\n3.Exit (End the Execution)");

printf ("\nEnter Your Choice: ");

scanf ("%d", &ch);

if (ch<1 || ch>3)

printf ("\nInvalid Choice, Please try again");

}while (ch<1 || ch>3);

switch (ch)

{case 1:

printf ("\nEnter the Element to be pushed : ");

scanf ("%d", &item);

printf (" %d", item);

push (stack, item);

if (status)

{ printf ("\nAfter Pushing ");

display (stack);

if (top == (MAX-1))

printf ("\nThe Stack is Full");

}

else

printf ("\nStack overflow on Push");

break;

case 2:

item = pop (stack);

if (status)

{ printf ("\nThe Popped item is %d. After Popping: ");

display (stack);

}

else

printf ("\nStack underflow on Pop");

break;

default:

printf ("\nEND OF EXECUTION");

}

}while (ch != 3);

getch();

}

Calculate reverse of a number

/* Program reverse number calculate */

#include<stdio.h>

#include<conio.h>

void main()

{

int n,digit, n1,rev=0;

clrscr();

printf("Enter the Any Integer No: ");

scanf("%d",&n);

n1=n;

while(n!=0)

{

digit = n%10;

rev= rev*10+digit;

n/=10;

}

printf("number is = %d :\n",n1);

printf("rev number = %d :",rev);

getch();

}

Convert octal number to decimal using while loop

/* Program read octal number and convert into decimal equi. */

#include<stdio.h>

#include<conio.h>

#include<math.h>

void main()

{

long int on,temp;

int dn=0,e=0,digit;

clrscr();

printf("Enter octal number : ");

scanf("%ld",&on);

temp=on;

while(on!=0)

{

digit= on%10;

dn+=digit*pow(8,e);

e++;

on/=10;

}

printf("octal number = %ld \n",temp);

printf("Decimal number= %d \n",dn);

getch();

}

Produce a pyramid of *s using for loop

/* display following pattern

***

*****

#include<stdio.h>

#include<conio.h>

void main()

{

int i,j,n;

clrscr();

printf("Enter no of line \n");

scanf("%d",&n);

for(i=0;i<n;i++)

{

for(j=1;j<=n-i;j++)

printf(" ");

for(j=1;j<=2*i-1;j++)

printf("*");

printf("\n");

}

getch();

}

Convert a binary number into decimal number using for loop

/* QN 10 PROGRAM READ A BINARY NUMBER AND CONVERT INTO DECIMAL NUMBER */

#include<stdio.h>

#include<conio.h>

main()

{ long int n1, n;

int dec=0,i=0,j,d;

clrscr();

printf("Enter the binary number :\n");

scanf("%ld",&n);

n1=n;

while(n!=0)

{ d = n%10;

dec=dec+d*pow(2,i);

n=n/10;

i++;

}

printf("\nBinary Number : %ld\nDecimal Number = %d ",n1,dec);

getch();

}

Read a string and display ASCII code of each Character

/* Read any string display ASCII code of each Charactres */

#include<stdio.h>

#include<conio.h>

#include<string.h>

void main()

{

int i,l,r;

char st[20];

clrscr();

printf("Enter any string");

gets(st);

l=strlen(st);

for(i=0;i<l;i++)

printf("%c\t Ascii code=%d\n",st[i],st[i]);

getch();

}

Count the total negative, positive and zero from a set of Integers

/* C Program: Read set of integer numbers and count

the total negative, Positive and zero */

#include<stdio.h>

#include<conio.h>

void main()

{

int x, n_count=0, p_count=0,z_count=0,i=0;

char ch;

clrscr();

{

printf("\nEnter an integer number -> ",++i);

scanf("%d",&x);

if(x<0) n_count++;

else if(x>0) p_count++;

else z_count++;

printf("\n\n\nAny more number <<y/>> ? ");

ch=getche();

}

while(ch=='y'||ch=='Y');

printf("\n\n");

printf("Total Negative Number : %d\n",n_count);

printf("Total Positive number : %d\n",p_count);

printf("Total Zero : %d\n",z_count);

getch();

}

Code for Program to print triangle inside square using * (stars)

#include<stdio.h>
#include<conio.h>
    
void main()
{
        int i,n,j,x;
        clrscr();
        printf("\n ENTER A VALUE: ");
        scanf("%d",&i);
        for(n=i;n>0;n--)
        {
            for(j=1;j<=n;j++)
            printf(" * ");
            for(j=i-n;j>=1;j--)
            printf("      ");
            for(x=n;x>=1;x--)
            printf(" * ");
            printf("\n");
        }
        for(n=0;n<i;n++)
        {
            for(j=0;j<=n;j++)
            printf(" * ");
            for(j=i-n;j>=2;j--)
            printf("      ");
            for(x=n;x>=0;x--)
            printf(" * ");
            printf("\n");
        }
            getch();
}


******************* OUTPUT *****************************************

     ENTER A VALUE: 5

     *  *  *  *  *  *  *  *  *  *
     *  *  *  *        *  *  *  *
     *  *  *              *  *  *
     *  *                    *  *
     *                          *
     *                          *
     *  *                    *  *
     *  *  *              *  *  *
     *  *  *  *        *  *  *  *
     *  *  *  *  *  *  *  *  *  *

Code for Program to print pyramid of * (starts) in reverse pattern

#include<stdio.h>
#include<conio.h>
void main()
{
        int i,n,j;
        clrscr();
        printf("\n Please Give The Value of N:  ");
        scanf("%d",&n);
        for(i=n;i>0;i--)
        {
            for(j=n-i;j>0;j--)
            printf("  ");
            for(j=2*i-1;j>0;j--)
            printf(" *");
            printf("\n");
        }
        getch();
}


****************************** OUTPUT *********************************

     Please Give The Value of N:  8


     * * * * * * * * * * * * * * *
       * * * * * * * * * * * * *
         * * * * * * * * * * *
           * * * * * * * * *
             * * * * * * *
               * * * * *
                 * * *
                   *

Reference Books

Download: C Programming Language, Second Edition

Download: C Language The Complete Reference, Fourth Edition

For C Programming Videos:

Link: C Programming Classes(Telugu)

Link: C Programming Classes(English)

Pages

C Language

WHAT IS C ?

Execution of C Program :

History of C :

Character Set :

Identifier :

Variable :

Keywords :

Escape Sequence Characters (Backslash Character Constants) in C:

Constants in C :

1. REAL CONSTANT :

2. INTEGER CONSTANT :

3. CHARACTER CONSTANT :

4. STRING CONSTANT :

Data Types in C :

* QUALIFIER :

* ENUM DATA TYPE :

* TYPEDEF :

Operators in C :

Operators Precedence and Associativity :

Decision Making Statements / Conditional Statements :

If Statement :

Program :

Output :

If-Else Statement :

Program :

Output :

Switch case Statement :

Program :

Output 1 :

Output 2 :

* RULES FOR DECLARING SWITCH CASE :

* ADVANTAGES OF SWITCH CASE :

Nested If-Else Statement :

Program :

Output :

Looping Statements / Iterative Statements :

* TYPES OF LOOPING STATEMENTS :

While loop :

Program :

Output :

For loop :

Program :

Output :

Do-While loop :

Program :

Output :

Break Statement :

Program :

Output :

Continue Statement :

Program :

Output :

Goto Statement :

Program :

Output :

Contents :

Functions in C :

Types of functions :

Program :

Output :

* Function Call By Passing Value

Program :

Output :

* Function Call By Returning Value

Program :

Output :

* Function Call By Passing and Returning Value

Program :

Output :

Advantages :

* Recursion (Recursive Function)

Program :

Output :

Features :

Advantages :

Disadvantages :

Note :

Storage Class :