DOCUMENT:Q59121  17-DEC-2000  [msdos]
TITLE   :How to Change the Way MS-DOS Allocates Memory
PRODUCT :Microsoft Disk Operating System
PROD/VER:MS-DOS:3.x,4.x,5.0
OPER/SYS:
KEYWORDS:

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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 
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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

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Keywords          :  
Technology        : kbMSDOSSearch kbMSDOS321 kbMSDOS400 kbMSDOS320 kbMSDOS330a kbMSDOS310 kbMSDOS500 kbMSDOS330 kbMSDOS401
Version           : MS-DOS:3.x,4.x,5.0

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