C/C++ if statement with Examples

Decision Making in C/C++ helps to write decision driven statements and execute a particular set of code based on certain conditions.

The C/C++ if statement is the most simple decision making statement. It is used to decide whether a certain statement or block of statements will be executed or not based on a certain type of condition.

Syntax:

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

Working of if statement

1. Control falls into the if block.
2. The flow jumps to Condition.
3. Condition is tested.
   1. If Condition yields true, goto Step 4.
   2. If Condition yields false, goto Step 5.
4. The if-block or the body inside the if is executed.
5. Flow steps out of the if block.

Flowchart

Note: If we do not provide the curly braces ‘{‘ and ‘}’ after if( condition ) then by default if statement will consider the immediate one statement to be inside its block. For example,

if(condition)
   statement1;
   statement2;

// Here if the condition is true,
// if block will consider only statement1
// to be inside  its block.

Example 1:

C

// C program to illustrate If statement

#include <stdio.h>

int main()
{
    int i = 10;

    if (i < 15) {
        printf("10 is less than 15 \n");
    }

    printf("I am Not in if");
}

C++

// C++ program to illustrate If statement

#include <iostream>
using namespace std;

int main()
{
    int i = 10;

    if (i < 15) {
        cout << "10 is less than 15 \n";
    }

    cout << "I am Not in if";
}

Output:

10 is less than 15 
I am Not in if

Dry-Running Example 1:

1. Program starts.
2. i is initialized to 10.
3. if-condition is checked. 10 < 15, yields true.
  3.a) "10 is less than 15" gets printed.
4. "I am Not in if" is printed.

Example 2:

C

// C program to illustrate If statement

#include <stdio.h>

int main()
{
    int i = 10;

    if (i > 15) {
        printf("10 is greater than 15 \n");
    }

    printf("I am Not in if");
}

C++

// C++ program to illustrate If statement

#include <iostream>
using namespace std;

int main()
{
    int i = 10;

    if (i > 15) {
        cout << "10 is greater than 15 \n";
    }

    cout << "I am Not in if";
}

Output:

I am Not in if