# C++ if-else Statements

The if-else statement is a conditional statement with an optional else. The if statement executes a block of statements is the condition is true, but does not do anything when condition is false. The if-else block contains code for both true and false conditions.

Each of the block in if-else construct will be enclosed using braces( { } ). The general form of if-else is given below.

if(expression)
{
statement1;
statement2;
}
else
{
statement3;
statement4;
}

Clearly, the a program executes if block when expression = true and executes else block when expression = false.

Example Program: if-else

// example program to demostrate if-else
#include <cstdlib>
#include <iostream>
using namespace std;
int main()
{
//Variable Declaration

int x,y,total;

//Variable Initialization

x = 100;
y = 200;
total = 0;

//the if-else block

if(x < 100)
{
total = x + y;
}
else
{
total = y - x;
}

//Printing the output

cout << "Total =" << total << endl;

system("PAUSE");
return EXIT_SUCCESS;
}

Output:

Total =100

In the above example, the condition x < 100 is false. As a result, the else block is executed giving an output 100.

## Types of if-else Constructs

There are several ways to construct if-else structure. Here is a list of possible constructs.

#1

if(expression)
{
statement1;
statement2;
}
else
{
statement3;
}

#2

if(expression)
{
if(expression)
{
statement1;
statement2;
}   else   {
statement3;
}
}
else
{
statement4;
}

#3

if(expression)
{
if(expression)
{
statement1;
}
else
{
statement2;
}
}
else
{
if(expression)
{
statement3;
}
else
{
statement4;
}
}

#4

if(expression)
{
}
else if(expression)
{
}
else if(expression)
{
}
else if(expression)
{
}

You can create different kinds of if-else constructs which one of the above construct as building blocks.

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