C Pocket Reference

Name

switch

Synopsis

In a switch statement, the value of the switch expression is compared to the constants associated with case labels. If the expression evaluates to the constant associated with a case label, program execution continues at the matching label. If no matching label is present, program execution branches to the default label if present; otherwise execution continues with the statement following the switch statement.

Syntax:

switch ( 
                     expression ) 
                     statement

The expression is an integer expression and statement is a block statement with case labels and at most one default label. Every case label has the form case const :, where const is a constant integer expression. All case constants must be different from one another.

Example:

switch( command )          // Query a command obtained
{                          // by user input in a menu, 
                           // for example.
  case 'a':
  case 'A': action1();     // Carry out action 1,
            break;         // then quit the switch.
  case 'b':
  case 'B': action2();     // Carry out action 2,
            break;         // then quit the switch.
  default:  putchar('\a'); // On any other "command":
                           // alert.
}

After the jump from the switch to a label, program execution continues sequentially, regardless of other labels. The break statement can be used to exit the switch block at any time. A break is thus necessary if the statements following other case labels are not to be executed.

Integer promotion is applied to the switch expression. The case constants are then converted to the resulting type of the switch expression.