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C `switch` Statement

C Decision

A switch statement allows testing a variable against multiple values. Each value is called a case, and the variable being tested is checked against each switch case.

Syntax

The syntax for a switch statement in C:

switch(expression){
    case constant-expression  :
       statement(s);
       break; /* Optional */
    case constant-expression  :
       statement(s);
       break; /* Optional */

    /* You can have any number of case statements */
    default : /* Optional */
       statement(s);
}

switch statements must follow these rules:

The expression in a switch statement is a constant expression and must be an integer or enumerated type.
A switch can have any number of case statements. Each case is followed by the value to be compared and a colon.
The constant-expression for a case must be the same data type as the variable in the switch, and it must be a constant or literal.
When the variable being tested equals the constant in a case, the statements following that case will execute until a break statement is encountered.
When a break statement is encountered, the switch terminates, and the control flow jumps to the next line following the switch statement.
Not every case needs to contain a break. If a case statement does not have a break, the control flow will continue into subsequent cases until a break is encountered.
A switch statement can have an optional default case, which must appear at the end of the switch. The default case can be used to perform a task when none of the cases are true. The break statement is not required in the default case.

Flowchart

Example

#include <stdio.h>

int main ()
{
   /* Local variable definition */
   char grade = 'B';

   switch(grade)
   {
   case 'A' :
      printf("Excellent!\n" );
      break;
   case 'B' :
   case 'C' :
      printf("Well done\n" );
      break;
   case 'D' :
      printf("You passed\n" );
      break;
   case 'F' :
      printf("Better try again\n" );
      break;
   default :
      printf("Invalid grade\n" );
   }
   printf("Your grade is %c\n", grade );

   return 0;
}

When the above code is compiled and executed, it produces the following result: