If else Statement in C Programming

Tech Area
April 25, 2024

In this tutorial, We will see how to use if and if else statement in C programming language.

C if Statement

The syntax of the if statement in C programming is:

if (test expression) 
{
   // code
}

How if statement works?

The if statement evaluates the test expression inside the parenthesis ().

If the test expression is evaluated to true, statements inside the body of if are executed.

If the test expression is evaluated to false, statements inside the body of if are not executed.

if statement

// Program to display a number if it is negative

#include<stdio.h>
#include<conio.h>
void main()
{
    int number;
    clrscr();
    printf("Enter an integer: ");
    scanf("%d", &number);

    // true if number is less than 0
    if (number < 0) {
        printf("You entered %d.\n", number);
    }

    printf("The if statement example.");
    getch();
}

Output 1

Enter an integer: -1
You entered -1.
The if statement example.

When the user enters -1, the test expression number<0 is evaluated to true. Hence, You entered –1 is displayed on the screen.

Output 2

Enter an integer: 2
The if statement example.

When the user enters 2, the test expression number<0 is evaluated to false and the statement inside the body of if is not executed

C if….else Statement

The if statement may have an optional else block. The syntax of the if..else statement is:

if (test expression) {
    // run code if test expression is true
}
else {
    // run code if test expression is false
}

How if…else statement works?

If the test expression is evaluated to true,

statements inside the body of if are executed.

statements inside the body of else are skipped from execution.

If the test expression is evaluated to false,

statements inside the body of else are executed.

statements inside the body of if are skipped from execution.

if….else statement

#include<stdio.h>
#include<conio.h>
void main()
{
    int age;
    clrscr();
    printf("Enter your age = ");
    scanf("%d", &age);

    // true if age is greater than and equal to 18
    if (age>=18) {
        printf("You can vote.");
    }
    else {
        printf("You can not vote.");
    }
    getch();
}

Output