Overview of if Statement

If the conditional expression is true, the target of the if will be executed; otherwise, the target of the else, if it exists, will be executed. At no time will both be executed.

The conditional expression controlling the if may be any type of valid C++ expression that produces a true or false result.

If the Boolean expression evaluates to true, then the block of code inside the 'if' statement will be executed.

Syntax of if statement:

if (condition/boolean expression)
{
     //Block of C++ statements here
     //These statements will only execute if the condition is true
}

In this statement, if condition is true then statement are execute and if is false, then statement are not execute.

Flow Diagram

Flow Diagram of if statement

 

Example

// ifdemo.cpp 
// demonstrates IF statement 
#include using namespace std;

int main()
  { 
    int x;

    cout > x;
    if( x > 100 )
    cout << “That number is greater than 100
”; return 0;
 } 

Output:

Enter a number: 2000
That number is greater than 100

Nested ifs

A nested if is an if statement that is the target of another if or else. Nested ifs are very common in programming.

The main thing to remember about nested ifs in C++ is that an else statement always refers to the nearest if statement that is within the same block as the else and not already associated with an else.

Syntax

if(i)
 {
   if(j) result = 1;
   if(k) result = 2;
 }