Files and Buffers Memory Usage (73843)

The information in this article applies to:
    Microsoft MS-DOS operating system 5.0
    Microsoft MS-DOS operating system 5.0a
    Microsoft MS-DOS operating system 6.0
    Microsoft MS-DOS operating system 6.2
    Microsoft MS-DOS operating system 6.21
    Microsoft MS-DOS operating system 6.22

This article was previously published under Q73843


The following article explains MS-DOS version 5.x and later files and buffers memory usage.



The version 5.0 "Microsoft MS-DOS User's Guide and Reference" states on page 376 that buffers are automatically loaded into the high memory area (HMA) when the DOS=HIGH statement is used in the CONFIG.SYS file.

The required 512 bytes (200h) is always loaded in conventional memory. This number remains constant regardless of the number of buffers specified.

If DOS=LOW, or no DOS= line exists in the CONFIG.SYS file, buffers are allocated in conventional memory. Each buffer uses approximately 532 bytes of memory.


The memory consumed by the FILES= statement in the CONFIG.SYS file is always allocated in conventional memory, regardless of the DOS= statement in the CONFIG.SYS file.

There is no constant number for the amount of memory used by each allocated file in the FILES= statement. As the number of files allocated increases, the amount of memory required for each file increases also. A chart of commonly used amounts follows:
   # Files in       Bytes used         Bytes used
   CONFIG.SYS       in Decimal           in Hex

     Default            192                 C0
        10              496                130
        15              608                260
        20              896                380
        25             1200                4B0
        30             1488                5D0
        35             1776                6F0
        40             2080                820
        45             2368                940
        50             2672                A70
        55             2960                B90
        60             3260                CC0
        65             3552                DE0
        70             3856                F10
        75             4144               1030

Modification Type: Major Last Reviewed: 5/12/2003
Keywords: KB73843