Using if statements in C++

1. Conditional Programming Using if 
Syntax:
if (conditional expression)
         Do something when expression evaluates true;
Example:
if (x == 100)
             cout << "x is 100 ";

2. Conditional Programming Using if … else
Syntax:
if (conditional expression)
          Do something when expression evaluates true;
else // Optional
          Do something elsewhen condition evaluates false;

Example:

if (x == 100)
             cout << "x is 100 ";

else

             cout << "x is not 100";

3. Executing Multiple Statements Conditionally

Syntax:

if (condition){

            // condition success block

           Statement 1;

           Statement 2;

}

else{

           // condition failure block

          Statement 3;

          Statement 4;

}

Example:

if (x >100)
{
     cout << "x > 100 ";
     cout << x;
}

else

{

     cout << "x <= 100 ";

     cout << x;

}

4. Nested if Statements

Syntax:

if (expression1)

{

        DoSomething1;

        if(expression2)

               DoSomething2;

        else

               DoSomethingElse2;

}

else

        DoSomethingElse1;

Example:

float mark;

cout<<"Input mark: "; cin>>mark;

if(mark>=0 && mark<=10){

      if(mark>=8.5)

               cout<<"A";

      else if(mark>=7.0)

               cout<<"B";

      else if(mark>=5.5)

               cout<<"C";

      else if(mark>=4.0)

               cout<<"D";

      else

               cout<<"F";

}

else

      cout<<"Mark wrong !";