Functions

Example

Write a function to check whether a given number is positive or negative.

void check(int num)
{
    if(num == 0)
        printf("Neither positive nor negative\n");
    else if(num > 0)
        printf("Positive\n");
    else
        printf("Negative\n");
}

where,

void - return type of a function

check - function name

int num - function parameter. We can give many parameters.

Statements between two curly braces {..} - function body

We will discuss more about above topics in upcoming tutorials.

Why do we need functions?

1.Improve Modularity

We can divide a large program into multiple small modules.

2.Code Reusability

Lets take an example,

Get two integer from user and check whether the two numbers are positive or negative.

Program without functions

#include<stdio.h>

int main()
{
    int num;

    //for first number
    scanf("%d",&num);

    if(num == 0)
        printf("Neither positive nor negative\n");
    else if(num > 0)
        printf("Positive\n");
    else
        printf("Negative\n");

    //for second number
    scanf("%d",&num);

    if(num == 0)
        printf("Neither positive nor negative\n");
    else if(num > 0)
        printf("Positive\n");
    else
        printf("Negative\n");

    return 0;
}

Here, we are writing the same piece of code again and again.

This is not a good program practice!

Lets rewrite it with functions.

Program with function

#include<stdio.h>

void check(int num)
{
    if(num == 0)
        printf("Neither positive nor negative\n");
    else if(num > 0)
        printf("Positive\n");
    else
        printf("Negative\n");
}

int main()
{
    int num;

    //for first number
    scanf("%d",&num);
    check(num);

    //for second number
    scanf("%d",&num);
    check(num);

    return 0;
}