Code Modules

A Code Module (or simply module) is a file containing XC=BASIC statements. An XC=BASIC program consists of one or more modules.

Note

Modules usually have the .bas extension, although the compiler does not care about the extension. The .bas extension is to help text editors to detect what kind of code you're editing.

Although completely optional, it is a good idea to organize code in multiple modules for better readability and maintainability if the program is growing exceedingly large.

Including modules

The INCLUDE directive instructs the compiler to load the given module, compile it, and "inject" the code into the current module at the exact point where the INCLUDE directive is.

main.bas

REM -- a simple game
INCLUDE "instructions.bas"
INCLUDE "play.bas"
CALL instructions ()
DO
  CALL gameplay ()
LOOP WHILE 1

instructions.bas

SUB instructions () SHARED STATIC
  PRINT "welcome. use joystick in port 2. press fire to jump."
END SUB

play.bas

SUB gameplay () SHARED STATIC
  ' actual game code here...
END SUB

The above example is a program that consists of three modules. The main module is main.bas and it includes two other modules, instructions.bas and play.bas.

As opposed to other languages, like C for example, you do not have to compile each module and have a linker to link them in one executable. You only have to compile the main module and the rest will be resolved by the compiler.

Note

Included modules are resolved recursively. You can include modules in included modules, to any depth.

Refer to the INCLUDE page to learn more - for example, how the compiler resolves the path of included modules.

Sharing identifiers among modules

Note

We'll use the term "identifier" to refer to variables, constants, subroutines and functions.

As you might have previously read here and here, variables, as well as constants, subroutines and functions, have three levels of visibility. The default visibility is GLOBAL, which means that the identifier is visible everywhere within the module where it was defined but not in other modules. The exception to this rule is when a variable or constant is defined within a subroutine or function. In this case, the default visibility is LOCAL.

To share an identifier with other modules, you must use the SHARED keyword. A few examples:

SHARED CONST PI = 3.14159
DIM a AS INT SHARED
SUB clear_screen () SHARED STATIC