If Statement in C

In this tutorial, we will learn about if statements in C. We will cover the basics of conditional execution using if statements.

What is an If statement

An if statement is a conditional statement that executes a block of code if a specified condition is true.

Syntax

The syntax for the if statement in C is:

if (condition) {
    // Code block to execute if condition is true
}

The if statement evaluates the specified condition. If the condition is true, the code block inside the if statement is executed; otherwise, it is skipped.

The following is the flowchart of how execution flows from start to the end of an if statement.

Flowchart of If Statement

Example 1: Checking if a Number is Even

  1. Declare an integer variable num.
  2. Assign a value to num.
  3. Use an if statement to check if num is even.
  4. Print a message indicating whether num is even or not.

C Program

#include <stdio.h>
int main() {
    int num = 10;
    if (num % 2 == 0) {
        printf("%d is even.\n", num);
    }
    return 0;
}

Output

10 is even.

Example 2: Checking if a Character is a Vowel

  1. Declare a character variable ch.
  2. Assign a value to ch.
  3. Use an if statement to check if ch is a vowel.
  4. Print a message indicating whether ch is a vowel or not.

C Program

#include <stdio.h>
int main() {
    char ch = 'a';
    if (ch == 'a' || ch == 'e' || ch == 'i' || ch == 'o' || ch == 'u' ||
        ch == 'A' || ch == 'E' || ch == 'I' || ch == 'O' || ch == 'U') {
        printf("%c is a vowel.\n", ch);
    }
    return 0;
}

Output

a is a vowel.

Example 3: Checking if a Number is Positive

  1. Declare an integer variable num.
  2. Assign a value to num.
  3. Use an if statement to check if num is positive.
  4. Print a message indicating whether num is positive or not.

C Program

#include <stdio.h>
int main() {
    int num = -5;
    if (num > 0) {
        printf("%d is positive.\n", num);
    }
    return 0;
}

Output