Global Instruction (Global); Extern Instruction (Uses) - HEIDENHAIN TNC 426 PB/M Technical Manual

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7.14.2 GLOBAL INSTRUCTION (GLOBAL)

GLOBAL <label, declaration beyond the file boundary>

Up to 1000 local labels are permitted in every file linked with USES. To enable

a module that was defined in a file to be called from another file, you must

declare the module to be global. This is done by entering the GLOBAL

instruction at the beginning of the file. You can set labels globally only if they

are defined with LBL (and not with KFIELD!) later on in the program.

The main program must not contain any GLOBAL definitions. A single label

cannot be declared global by more than one module. However, a name that is

declared global in file A can be used again locally in file B. Altogether,

1000 labels may be as defined as global in all modules.

EXTERN <label, a module from another file can now be called

with a CM command>

To enable a label in one file to access modules that other files have declared

as GLOBAL, you must declare the label with EXTERN. You must write the

EXTERN instruction at the beginning of the file. In the program code you can

then jump to this label with the commands CM, CMT and CMF.

The following functions are not permitted with external labels:

JP, JPF, JPT

Access to a constants field

Linking a CM instruction in a CASE branch

The name of the external label cannot be used again as a local label in the

same file. Every external label reduces the number of local labels that remain

HEIDENHAIN Technical Manual TNC 426, TNC 430