return statement in C

A function is a collection of statements grouped together to do some specific task. It may return a value. However, in no case a function will return more than one value. What does it mean by returning a value and where it is returned? To understand this let us consider an example.

Suppose I am the boss of a company. I assigned an audit task to one of my employee. Consider the audit task as a function. Employee will complete the task (execute the function) and return the audit report back to the boss (i.e. me). Similarly, function returns a value and program control back to the caller function.

Use of return statement

return statement terminates a function and transfer program control to its caller function. Optionally it may return a value to the caller. You can use the return statement anywhere inside a function.

Note: Once a function returned program control to the caller. The function cannot get the control back.

Syntax of return statement

return expression;

• return keyword transfers program control to the caller.
• expression is optional, used to return result of a valid C expression to the caller.

Note: The function return type and returned value type (data type) of the function must be same.

Example program to use return statement

Write a C program to input two numbers from user. Write a function to find maximum between two given two numbers and return the maximum value.

/**
 * C program to find maximum between two numbers using function
 */

#include <stdio.h>

/* Function declaration */
int max(int num1, int num2);

int main()
{
    int num1, num2, maximum;
    printf("Enter two numbers: ");
    scanf("%d%d", &num1, &num2);

    /*
     * Call max function with arguments num1 and num2
     * Store the maximum returned to variable maximum
     */
    maximum = max(num1, num2);

    printf("Maximum = %d", maximum);

    return 0;
}

/* Function definition */
int max(int num1, int num2)
{
    int maximum;

    // Find maximum between two numbers
    if(num1 > num2)
        maximum = num1;
    else
        maximum = num2;

    // Return the maximum value to caller
    return maximum;
}

Output –

Enter two numbers: 10 20
Maximum = 20