UNDEFINE/DEFINE Example

UNDEFINE/DEFINE Example

Directives highlighted in this example are:

• #undefine

#define

Program Functional Description

This example shows the the usage of #UNDEFINE directive. A symbol name previously defined with the #DEFINE directive, is removed from the symbol table if #UNDEFINE directive is used. The same symbol may be redefined again.

Commented Code Listing

list p=16f877 ;Select the device.

#include <p16f877.inc> ;Include standard header file

;for the selected device.

area set 0 ;The label 'area' is assigned

;the value 0.

#define lngth 50H ;Label 'lngth' is assigned

;the value 50H.

#define wdth 25H ;Label 'wdth' is assigned

;the value 25H

area set lngth*wdth ;Reassignment of label 'area'.

;So 'area' will be reassigned a

;value equal to 50H*25H.

#undefine lngth ;Undefine label 'lngth'.

#undefine wdth ;Undefine label 'wdth'

#define lngth 0 ;Define label 'lngth' to '0'.

end