User manual

228

mikoC PRO for dsPIC

MikroElektronika

Auto

The auto storage-class specier declares an automatic variable (a variable with a local lifetime). An auto variable is

visible only within the block in which it is declared.

The auto storage-class specier can only be applied to names of variables declared in a block or tonames of function

parameters.

However, these names have automatic storage by default. Therefore the auto storage class specier is usually

redundant in a data declaration.

The register storage-class specier is used to dene local variables that should be stored in a register instead of RAM.

At the moment this modier has no special meaning in mikroC PRO for dsPIC30/33 and PIC24.

mikroC PRO for dsPIC30/33 and PIC24 simply ignores requests for register allocation.

Static

The static storage class specier lets you dene variables or functions with internal linkage, which means that each

instance of a particular identier represents the same variable or function within one le only.

In addition, variables declared static have static storage duration, which means that memory for these variables is

allocated when the program begins running and is freed when the program terminates.

Static storage duration for a variable is different from le or global scope. A variable can have static duration, but local

scope.

Extern

The extern storage class specier lets you declare objects that can be used in several source les. An extern declaration

makes a described variable usable by the succeeding part of the current source le.

This declaration does not replace the denition. It is used to describe a variable that is externally dened. An extern

declaration can appear outside a function or at the beginning of a block.

If the declaration describes a function or appears outside a function and describes an object with external linkage, the

keyword extern is optional.

If a declaration for an identier already exists within the le scope, any extern declaration of the same identier found

within a block refers to the same object.

If no other declaration for the identier exists within the le scope, the identier has external linkage.

See Linkage for more information.