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C User-defined functions

C User-defined functions
C User-defined functions


C User-defined functions

In this tutorial, you will learn to make user-defined functions in C programming with the help of an example.

A function is a block of code that performs a particular task.

C allows you to define functions as per your need. These functions are known as user-defined functions. For instance:

Assume, you have to make a circle and shading it relying on the sweep and shading. You can make two functions to solve this issue:

createCircle() function
color() function

Example: User-defined function

Here is an example to add two integers. To perform this task, we have created a user-defined addNumbers().

#include <stdio.h>
int addNumbers(int a, int b);         // function prototype

int main()
    int n1,n2,sum;

    printf("Enters two numbers: ");
    scanf("%d %d",&n1,&n2);

    sum = addNumbers(n1, n2);        // function call
    printf("sum = %d",sum);

    return 0;

int addNumbers(int a, int b)         // function definition   
    int result;
    result = a+b;
    return result;                  // return statement

Function prototype

A function prototype is essentially the declaration of a function that indicates the function’s name, parameters and bring type back. It doesn’t contain a function body.

A function prototype offers data to the compiler that the capacity may later be utilized in the program.

Syntax of function prototype

returnType functionName(type1 argument1, type2 argument2, ...);

In the above example, int addNumbers(int a, int b); is the function prototype which provides the following information to the compiler:

name of the function is addNumbers()
the return type of the function is int
two arguments of type int are passed to the function
The function prototype is not needed if the user-defined function is defined before the main() function.

Calling a function

Control of the program is transferred to the user-defined function by calling it.

Syntax of function call

functionName(argument1, argument2, ...);

In the above example, the function call is made using addNumbers(n1, n2); statement inside the main() function.

Function definition

Function definition contains the block of code to perform a specific task. In our example, adding two numbers and returning it.

Syntax of function definition

returnType functionName(type1 argument1, type2 argument2, ...)
    //body of the function

When a function is called, the control of the program is moved to the function definition. What’s more, the compiler begins executing the codes inside the body of a function.

Passing arguments to a function

In programming, argument refers to the variable passed to the function. In the above example, two variables n1 and n2 are passed during the function call.

The parameters a and b accepts the passed arguments in the function definition. These arguments are called formal parameters of the function.

pass arguments c programming

The type of arguments passed to a function and the formal parameters must match, otherwise, the compiler will throw an error.

If n1 is of char type, and also should be of char type. If n2 is of float type, variable b also should be of float type.

A function can also be called without passing an argument.

Return Statement

The return statement terminates the execution of a function and returns an incentive to the calling capacity. The program control is moved to the calling capacity after the return statement.

In the above example, the value of the result variable is returned to the main function. The sum variable in the main() function is assigned this value.

c return statement
Syntax of the return statement
return (expression);

For example,

return a;
return (a+b);

The type of value returned from the function and the return type specified in the function prototype and function definition must match.

Please feel free to give your comment if you face any difficulty here.

salman khan

Written by worldofitech

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