Q31821: Structured Programming in Microsoft QuickBASIC - Modules

Article: Q31821
Product(s): See article
Version(s): 1.00 1.01 1.02 2.00 2.01 3.00 4.00 4.00b 4.50
Operating System(s): MS-DOS
Keyword(s): ENDUSER | | mspl13_basic
Last Modified: 20-DEC-1989

Easy modular programming is possible with Microsoft QuickBASIC by
using separately compiled modules. BASIC programs no longer have to be
developed as one large program; they can be written as separate,
functionally grouped sets of subroutines that can be used in other
programs.

A module consists of an optional "main program" and a set of
subprogram procedures. Data can be passed between linked modules by
using subprogram parameters or named COMMON SHARED blocks. The named
COMMON SHARED statement allows different groups of variables and
arrays to be shared among the various modules in a single program. An
example of a common block named GRAF3D is shown below:

   DIM TRANSFORM3D(3,3) 'static array passed in COMMON
   COMMON SHARED /GRAF3D/ CURX, CURY, CURZ, TRANSFORM3D()

The SHARED attribute of the COMMON statement shares that COMMON among
all subprogram procedures in that particular module. The variables in
a COMMON without the SHARED attribute are only available at the main
program level.

An unnamed (blank) COMMON statement can pass information between
CHAINed programs. (Named COMMON blocks are not carried across when you
CHAIN to another QuickBASIC .EXE program.)

Subprograms, separate compilation, COMMON blocks, and program CHAINing
make Microsoft QuickBASIC a useful language for developing large
application systems.

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