Switch statements are a special type of branching mechanism that only checks if the value of a variable is equal to one of several values. Switch statements can be useful when implementing a menu in a program, or something else where you only have a few, finite, discrete options.

In C++, switch statements only work with primitive data types, like integers and chars - not strings.

switch ( VARIABLE )
{
 case VALUE1:
   // Do thing
 break;

 case VALUE2:
   // Do thing
 break;

 default:
  // Default code
}

With a switch statement, each case is one equivalence expression. The default case is executed if none of the previous cases are.

case VALUE1: // equivalent to: if ( VARIABLE == VALUE1 )

case VALUE2: // equivalent to: if ( VARIABLE == VALUE2 )

break: // required at the end of a case statement (unless...)

default: // equivalent to: else

The default case is not required, just like how the else clause is not required in an if statement.

The end of each case should have a break; statement at the end. If the break is not there, then it will continue executing each subsequent case's code until it does hit a break.

This behavior is "flow-through", and it can be used as a feature if it matches the logic you want to write.

If you're declaring a variable within a case statement, you need to enclose your case with curly braces { }, otherwise you'll get compiler errors:

switch ( operation )
{
 case 'A':
   {
     float result = num1 + num2;
     cout << "Result: " << result << endl;
   }
  break;
}

Perhaps you are implementing a calculator, and want to get an option from the user: (A)dd, (S)ubtract, (M)ultiply, or (D)ivide. You could store their choice in a char variable called operation and then use the switch statement to decide what kind of computation to do:

switch ( operation )
{
 case 'A': // if ( operation == 'A' )
  result = num1 + num2;
  break;

 case 'S': // else if ( operation == 'S' )
  result = num1 - num2;
  break;

 case 'M': // else if ( operation == 'M' )
  result = num1 * num2;
  break;

 case 'D': // else if ( operation == 'D' )
  result = num1 / num2;
  break;
}

cout << "Result: " << result << endl;

Sometimes you want to check if your variable equals a value "x" or "y", and execute the same code for each. You can use flow-through in this case. If no break; is given for a specific case, then it will continue to execute code for the following case until a break; is found.

char choice;
cout << "Do you want to quit? (Y/N): ";
cin >> choice;

switch ( choice )
{
 case 'Y':
 case 'y':
  done = true;
  break;

case 'N':
case 'n':
  done = false;
  break;

default:
  cout << "Unknown selection!" << endl;
}

switch( option )
{
    case 'X':
        cout << "RESULT 1" << endl;
    break;

    case 'Y':
        cout << "RESULT 2" << endl;
    break;

    case 'Z':
        cout << "RESULT 3" << endl;
    break;

    default:
        cout << "RESULT 4" << endl;
}

switch( option )
{
    case 'X':
        cout << "RESULT 1" << endl;

    case 'Y':
        cout << "RESULT 2" << endl;

    case 'Z':
        cout << "RESULT 3" << endl;

    default:
        cout << "RESULT 4" << endl;
}