Switch

A switch statement provides a means of checking an expression against various case statements. If there is a match, the code within starts to execute. The break keyword can be used to terminate a case.

There’s also an optional default statement marking code that executes if none of the case statements are true.

Syntax

A switch statement looks like:

switch (grade) {
  case 9:
    std::cout << "Freshman\n";
    break;
  case 10:
    std::cout << "Sophomore\n";
    break;
  case 11:
    std::cout << "Junior\n";
    break;
  case 12:
    std::cout << "Senior\n";
    break;
  default:
    std::cout << "Invalid\n";
    break;
}

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• The switch keyword initiates the statement and is followed by (), which contains the value that each case will compare. In the example, the value or expression of the switch statement is grade. One restriction on this expression is that it must evaluate to an integral type (int, char, short, long, long long, or enum).
• Inside the block, {}, there are multiple cases.
• The case keyword checks if the expression matches the specified value that comes after it. The value following the first case is 9. If the value of grade is equal to 9, then the code that follows the : would run.
• The break keyword tells the computer to exit the block and not execute any more code or check any other cases inside the code block.
• At the end of each switch statement, there is a default statement. If none of the cases are true, then the code in the default statement will run.

In the code above, suppose grade is equal to 10, then the output would be “Sophomore”.

Note: Without the break keyword at the end of each case, the program would execute the code for the first matching case and all subsequent cases, including the default code. This behavior is different from if/else conditional statements which execute only one block of code.

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