Mikroelektronika MIKROE-442 Datenbogen

mikroBasic PRO for dsPIC30/33 and PIC24

MikroElektronika

193

Visibility

The  visibility  of  an  identifier  is  that  region  of  the  program  source  code  from  which  legal  access  to  the  identifier’s 

associated object can be made.

Scope  and  visibility  usually  coincide,  though  there  are  circumstances  under  which  an  object  becomes  temporarily 

hidden by the appearance of a duplicate identifier, i.e. the object still exists but the original identifier cannot be used to 

access it until the scope of the duplicate identifier is ended.

Technically, visibility cannot exceed scope, but scope can exceed visibility.

Name space is a scope within which an identifier must be unique. The mikroBasic PRO for dsPIC30/33 and PIC24 uses 

two distinct categories of identifiers:

 

1. Global variables are visible throughout the whole unit, from the place of declaration. Also. they can be  

 

    seen in other units, if they are declared above the Implementation section. 

 

2. Local variables, parameters, types, function results - must be unique within the block in which they are  

 

    declared. 

For example:

dim level as byte

sub procedure control(dim sens as byte)

  dim location as byte

  location = 1

  sens = location

  level = 123

sub procedure temperature

  location = 0      ‘ ILLEGAL

  sens = 23         ‘ ILLEGAL: redefinition of sens

  level = 95

Identifier is declared in the declaration section of 

the main module, out of any function or procedure

Scope extends from the point where it is declared to the end of the current 

file, including all routines enclosed within that scope. These identifiers have 

a file scope and are referred to as globals.

Identifier is declared in the function or procedure

Scope extends from the point where it is declared to the end of the current 

routine. These identifiers are referred to as locals.

Identifier is declared in the interface section of the 

module

Scope extends the interface section of a module from the point where it 

is declared to the end of the module, and to any other module or program 

that uses that module. The only exception are symbols which have a scope 

limited to the file in which they are declared.

Identifier is declared in the implementation section of 

the module, but not within any function or procedure

Scope extends from the point where it is declared to the end of the module. 

The identifier is available to any function or procedure in the module.