DSWAP Increases by 16 Bytes Each Time an MS-DOS Program Is Run

 Last reviewed: November 21, 1994
Article ID: Q93045
The information in this article applies to:
  • Microsoft Windows operating system versions 3.1, 3.11
  • Microsoft Windows for Workgroups versions 3.1, 3.11

Each time you run an MS-DOS-based application in standard mode of either Windows or Windows for Workgroups, the size of DSWAP.EXE in memory increases by 16 bytes. This guarantees that each MS-DOS session starts at a unique address.

MS-DOS keeps track of per-process information such as open files using the address of the program segment prefix. If the size of DSWAP did not increase, two MS-DOS-based applications could be started with the same program segment prefix, and the system would have difficulty distinguishing between them.

KBCategory: kbother
KBSubcategory: wfw wfwg win31
Additional reference words: 3.10

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Last reviewed: November 21, 1994
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