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if Statement in C Programming

Decision Making in C

In this lesson, we will understand what if statement is and how to use it in C programming along with some example.

What is if Statement

The if statement is the most simple decision making statement in C programming. Using if statement we test some condition, if the condition is true then a block of statements is executed otherwise not.

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if Statement Syntax

if(condition)
{
    /* Statements to execute if
    condition is true */
}

In the above syntax inside the brackets ( ) of if statement we will write our condition. If the condition is true then the statements written within the curly braces { } of if statement will execute otherwise not. We can write our condition using Arithmetic, Relational and Logical operators.

Now let's see some examples for more understanding.

Example 1 (Condition using Relational operator)

C program to check if an integer variable's value is greater than 10.

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

int main()
{
    int a=25;
    if(a>10)
    {
        printf("Yes %d is greater than 10",a);
    }
    return 0;
}

Output

Yes 25 is greater than 10

Here you can see that the condition (a>10) is true because the value of a is greater than 10. So the statement which is written inside the curly braces of if statement has executed and the output is printed on the screen.

Example 2 (Condition using Arithmetic and Relational operator)

C program to check if the sum of 2 integer variable's value is greater than 10.

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

int main()
{
    int a=10, b=5;
    if(a+b>10)
    {
        printf("Yes %d is greater than 10",a+b);
    }
    return 0;
}

Output

Yes 15 is greater than 10

Here you can see that we have used Arithmetic and Relational operator in the condition (a+b>10) and the condition is also true because the value of a+b is greater than 10. So the statement which is written inside the curly braces of if statement has executed and the output is printed on the screen.

Example 3 (Condition using Arithmetic, Relational and Logical operator)

C program to check if an integer variable's value is an even number and is also greater than 10.

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

int main()
{
    int a=18;
    if(a%2==0 && a>10)
    {
        printf("%d is an even number and is also greater than 10",a);
    }
    return 0;
}

Output

18 is an even number and is also greater than 10

Here you can see that we have used Arithmetic, Relational and Logical operator in the condition (a%2==0 && a>10) and both the conditions a%2==0 and a>0 are also true because the remainder of the modulus division a%2 is equal to 0 and also value of a is greater than 10. So the statement which is written inside the curly braces of if statement has executed and the output is printed on the screen.