Q31153: LINK Overlays Not Supported in BASIC 6.00/6.00b, or QuickBASIC

Article: Q31153
Product(s): See article
Version(s): 6.00 6.00b
Operating System(s): MS-DOS
Keyword(s): ENDUSER | docerr B_QuickBas | mspl13_basic
Last Modified: 30-MAY-1990

Microsoft QuickBASIC versions 1.00, 1.02, 2.00, 2.01, 3.00, 4.00,
4.00b, and 4.50 for MS-DOS and Microsoft BASIC Compiler versions 6.00
and 6.00b for MS-DOS do NOT support code overlays. These versions of
BASIC compiler and QuickBASIC are not designed to output the special
object format necessary to support overlays under MS-DOS.

The description of LINK.EXE provided in the "Microsoft CodeView and
Utilities: Software Development Tools for MS-DOS" manual, supplied
with Microsoft BASIC Compiler versions 6.00 and 6.00b, is a general
description for the linker. However, this description is misleading.
Although Pages 285-286 discuss linker overlays, overlays are not
supported by these versions of BASIC.

Microsoft has introduced support for linker overlays in Microsoft
BASIC Professional Development System (PDS) version 7.00 under MS-DOS.
For more information, search for a separate article with the following
words:

   how and use and LINK and overlays and BASIC and PDS and 7.00

Other Microsoft languages, such as Microsoft C and Microsoft FORTRAN,
also support linker overlays.

The error message "L2048 cannot find overlay manager" will be
generated if you try to link with overlays using BASIC compiler
version 6.00.

Overlays are useful in a memory-restricted environment because overlay
capability allows programs to load portions of code from disk into
memory when needed, and overlays in memory not currently being used
are automatically swapped out when loading the needed overlays.

The CHAIN, RUN, and SHELL statements in BASIC offer capabilities that
are similar to code overlays, but more limited.

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