Q59121: How to Change the Way MS-DOS Allocates Memory
Article: Q59121
Product(s): Microsoft Disk Operating System
Version(s): MS-DOS:3.x,4.x,5.0
Operating System(s):
Keyword(s):
Last Modified: 17-DEC-2000
-------------------------------------------------------------------------------
The information in this article applies to:
- Microsoft MS-DOS operating system versions 3.1, 3.2, 3.21, 3.3, 3.3a, 4.0, 4.01, 5.0
-------------------------------------------------------------------------------
SUMMARY
=======
When MS-DOS allocates memory for your program, it uses a first-fit allocation
strategy by default. You can change MS-DOS's default strategy to a best fit,
last fit, or back to first fit with a call to INT 21h Function 58h.
MORE INFORMATION
================
A first-fit strategy forces MS-DOS to search from low addresses in memory to
high addresses, and allocate the first available block of memory large enough
for the requested allocation.
A best-fit strategy forces MS-DOS to search all addresses in memory and allocate
the smallest block still large enough to fill the requested allocation.
A last-fit strategy forces MS-DOS to search from high addresses in memory to low
addresses, and allocate the first available block of memory large enough for the
requested allocation.
The best-fit algorithm is the slowest to execute since all free memory is
searched, but results in the least memory fragmentation during multiple
allocations and frees. Conversely, the first-fit and last-fit strategies are
fastest to execute but result in a higher degree of memory fragmentation.
Additional query words: 3.00 3.10 3.20 3.21 3.22 3.30 3.30a 4.00 4.00a 4.01 5.00 noupd
======================================================================
Keywords :
Technology : kbMSDOSSearch kbMSDOS321 kbMSDOS400 kbMSDOS320 kbMSDOS330a kbMSDOS310 kbMSDOS500 kbMSDOS330 kbMSDOS401
Version : MS-DOS:3.x,4.x,5.0
=============================================================================
THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.
Copyright Microsoft Corporation 1986-2002.