Mikroelektronika MIKROE-738 Datenbogen

mikroC PRO for PIC32

MikroElektronika

251

Note:  

#if 

and

 #else

 preprocessor statements (directives) look similar to

 if

 and 

else

 statements, but have  

 

 

very different effects. They control which source file lines are compiled and which are ignored.

The 

switch

 statement is used to pass control to a specific program branch, based on a certain condition. The syntax 

of the 

switch

 statement is:

switch (expression) {

  case constant-expression_1 : statement_1;

    .

    .

    .

  case constant-expression_n : statement_n;

  [default : statement;]

}

First, the 

 (condition) is evaluated. The 

switch

 statement then compares it to all available 

 following the keyword 

case

. If a match is found, 

switch

 passes control to that matching 

case

 causing 

the 

 

following the match evaluates. Note that 

 must evaluate to integer. It is not 

possible to have two same constant expressions evaluating to the same value.

Parentheses around 

 are mandatory.

Upon finding a match, program flow continues normally: the following instructions will be executed in natural order 

regardless of the possible 

case

 label. If no 

case

 satisfies the condition, the 

default

 case evaluates (if the label 

default

 is specified).

For example, if a variable

 i

 has value between 1 and 3, the following switch would always return it as 4:

switch (i) {

  case 1: i++;

  case 2: i++;

  case 3: i++;

}

To avoid evaluating any other cases and relinquish control from 

switch

, each 

case

 should be terminated with break.

Here is a simple example with 

switch

. Suppose we have a variable 

phase

 with only 3 different states (0, 1, or 2) and a 

corresponding function (event) for each of these states. This is how we could switch the code to the appopriate routine:

switch (phase) {

  case 0: Lo();  break;

  case 1: Mid(); break;

  case 2: Hi();  break;

  default: Message(“Invalid state!”);

}