• On July 1, 2025
• By Karmehavannan
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• Categories: function in C
• Tags: User defined function

function in C programming language with example

Functions in C programming language with example

In the tutorial, we will discuss function in C programming language with examples. The function is the building block of programming in C language.

function in C programming language

Description

Description of function in C programming language

What is a function?

The function is a block of statement or instruction enclosed by curly braces { } that together perform one of the special tasks in  C program. Collection of these functions perform a special purpose(inter-connected a lot of tasks) in C program.

return_type function_name (parameter list){
//function  body
return (expression)
}

 

Explanation of function

return_type – The return type is a data type used for the function declaration.

Ex – int, float, double, void

Void data type never returns any value but the usage of other data type returns the value.

function_name – function name is used to identify the function in the C Programming language. Every function should have a name(user define function) as the function name represents the uniqueness of function and function name is used to call the function.

parameter_list – A function may contain a parameter list(one or more parameter). Sometimes, functions may not contain a parameter(it is optional). However, when a function is executed, you pass a value(it’s called argument) to the parameter list which refers to the parameter type, order of parameter and number of the parameter of a function.

Function_body – The body of the function consists of a group of statements. They will be invoked when the function is called.

Type of functions in C language

Two types of function available in C language.

Standard library function – standard library functions are built-in functions or predefined functions in C language to handle a special task.

Ex – mathematical operations, I/O processing and string handling etc

These functions are already defined in the header file of C programming language. When they are included in the header file of the program, we can use these function easily.

Ex –

string.h – string handling functions

math.h – Arithmetic operations

The printf()  function is a predefined function in C language used to get the output on the screen. This function is defined in “stdio.h” header file.

The scanf()  function is a predefined function in C language used to get the input from the user. This function is defined in “stdio.h” header file.

User defined function in C language

C language supports you to define functions according to your needs and satisfaction. These functions are called as user-defined functions in C language

 

4 type of function available in C Language

• Function with no argument and no return value
• Function with no argument and with return value
• Function with  argument and no return value
• Function with  argument and return value

Examples

1. void add() //No return without argument
2. void sub(int,int)//No return argument
3. int mul() //Return without argument
4. float div(int ,int) //Return with argument

Add two  numbers using function(No return without argument)

#include <stdio.h>
#include <stdlib.h>
void add(); //function declaration
void main()
{
add();          //calling function no argument
getch();
    return 0;
}
void add()//no argument is passed to this function
{//void data type never return anything from function
    int a,b;
     printf("Enter first number for a");
     scanf("%d",&a);
     printf("Enter second number for b");
     scanf("%d",&b);
     int c=a+b;
     printf("total value (a+b) is %d\n",c);

}

 

When the above program is compiled and run, it will produce the following result

Enter first number for a :45
Enter second number for b :78
Total value (a+b) is 123

 

Calculating the difference between two  numbers using function(No return with argument)

#include <stdio.h>
#include <stdlib.h>
 void sub(int f_num, int s_num);//function declaration
int main()
{
sub(67,34);
getch();
    return 0;
}
void sub(int f_num, int s_num) //No argument is passed to this function
{   //void data type never return value from function
    printf("Enter the first number of a: ");
    scanf("%d",&f_num);
    printf("Enter the first number of b: ");
    scanf("%d",&s_num);
    int diff=f_num-s_num;
    printf("Total value(a+b) is %d\n",diff);
}

 

When the above program is compiled and run, it will produce the following result

Enter your first number :67
Enter your second number :34
Different between two numbers :33

 

Multiplication of  two  numbers using function(Return without argument)

#include <stdio.h>
#include <stdlib.h>
 int mul();//function declaration
int main()
{
    printf("Answer is: %d",mul());
getch();
    return 0;
}
int mul() //No argument is passed to this function
{   //void data type never return value from function
    int f_no, s_no;
    printf("Enter the first number of f_no: ");
    scanf("%d",&f_no);
    printf("Enter the first number of s_no: ");
    scanf("%d",&s_no);
   return f_no*s_no;
}

 

 

When the above program is compiled and run, it will produce the following result

Enter first number for f_no:12
Enter second number for s_no:23
Answer is :276

 

Multiplication of  two  numbers using function(Return with arguments

#include <stdio.h>
#include <stdlib.h>
 int mul(int a, int b);//function declaration
int main()
{
    printf("The result is: %d",mul(45,34));//function calling
getch();
    return 0;
}
int mul(int f_no, int s_no) //No argument is passed to this function
{   //void data type never return value from function

    printf("Enter the first number of f_no: ");
    scanf("%d",&f_no);
    printf("Enter the first number of s_no: ");
    scanf("%d",&s_no);
   return f_no*s_no;//return statements in function
}

 

When the above program is compiled and run, it will produce the following result

The first number of f_no: 45
The second number of s_no: 100
The result is :4500

 

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