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 <iostream>
using namespace std;
int main() {
    int num = 10;
    if (num % 2 == 0) {
        cout << num << " is even.";
    }
    return 0;
}

Output

10 is even.

Example 2: Checking if a String Starts with a Specific Value

  1. Declare a string variable str.
  2. Assign a value to str.
  3. Use an if statement to check if str starts with a specific value.
  4. Print a message indicating the result of the check.

C++ Program

#include <iostream>
#include <string>
using namespace std;
int main() {
    string str = "Hello, world!";
    if (str.substr(0, 5) == "Hello") {
        cout << "String starts with 'Hello'.";
    }
    return 0;
}

Output

String starts with 'Hello'.

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 <iostream>
using namespace std;
int main() {
    int num = -5;
    if (num > 0) {
        cout << num << " is positive.";
    }
    return 0;
}

Output