Unlocking Large-Model Extra Data Segments
ID: Q83363
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The information in this article applies to:
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Microsoft Windows Software Development Kit (SDK) versions 3.0, 3.1
SUMMARY
An application that is compiled using the large memory model can have
multiple code segments and multiple data segments.
Under Windows 3.0, all the data segments except for the first one (the
so called "extra" data segments) are loaded into memory segments that
are fixed and page locked. Fixed and page locked segments interfere
with effective memory management. They reduce the amount of free
memory addressed below 1 megabyte (MB) in the linear address space,
and in some cases, cause out-of-memory errors as additional
applications are run.
Under Windows 3.1, extra data segments are loaded into movable memory
and the above difficulties with fixed and page locked segments do not
apply.
A large model application can change the attributes of its extra data
segments by calling the GlobalPageUnlock and GlobalUnfix functions.
However, to do this effectively, the application must be able to
enumerate the selectors for its extra data segments.
Largeapp.exe is a file in the Microsoft Software Library that demonstrates
using the GlobalPageUnlock and GlobalUnfix functions to change the
attributes of an application's extra data segments. Largeapp.exe contains
the source code to two applications: Largeapp.exe, which is a large-model
application for the Windows environment, and SYMSEG, which is an MS-DOS
(non-Windows) application.
SYMSEG is a utility that reads a symbol file produced by the Microsoft
Linker, and creates a table of the data segments in an application.
LARGEAPP uses the information from this table to enumerate its own
data segments.
MORE INFORMATION
The following files are available for download from the Microsoft
Download Center. Click the file names below to download the files:
Largeapp.exe
For more information about how to download files from the Microsoft
Download Center, please visit the Download Center at the following Web
address
http://www.microsoft.com/downloads/search.asp
and then click How to use the Microsoft Download Center.
LARGEAPP determines the version of Windows under which it is running.
The segment attributes must be changed only if the application is
running under Windows 3.0.
Additional query words:
softlib LARGEAPP.ZIP
Keywords : kbfile kbsample kb16bitonly kbWinOS310 kbWinOS300 KrModls
Version : WINDOWS:3.0,3.1
Platform : WINDOWS
Issue type :