Understanding the Settings in the Windows Millennium Edition Config.sys File (274646)

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One of the features in a legacy-free Windows Me environment is that the Io.sys file does not process either the Config.sys or the Autoexec.bat file. However, these files are scanned for changes to environment variables that must be imported because the files contain various settings and preferences that configure the "global environment" for the computer during the boot phase and when you start a new MS-DOS Virtual Machine (VM). When user environment settings are imported from the Config.sys file to the registry, any line in the Config.sys file that begins with one of the following directives is ignored: Note that the SET and MENU directives are not ignored.

Description of Certain Settings

• Setting: LASTDRIVE
  Default Value: Z
  User Configurable: No
  This setting specifies the last drive letter that is available to any MS-DOS Virtual Machine (VM). This setting does not affect Windows-based 32-bit programs, virtual device drivers (VxDs), or Windows Driver Model (WDM) drivers, all of which have 26 drive letters available.
• Setting: FCBS
  Default Value: 4
  User Configurable: No
  This setting controls the number of File Control Blocks (FCBS) that are available to each MS-DOS VM. However, MS-DOS-based programs that were written after the release of MS-DOS 2.0 use file handles rather than FCBS.
• Setting: FILES
  Default Value: 30
  User Configurable: Yes
  You cannot set the FILES value, the first five handles in the handle table, or the standard handles (STDIN, STDOUT, STDERR, STDAUX, and STDPRN) by using the Config.sys file. The remaining 25 handles are available for new file handles. MS-DOS-based programs that require more than 30 open file handles must use the PerVMFiles setting.For additional information about the PerVMFiles setting, click the article number below to view the article in the Microsoft Knowledge Base:

  269030 How to Increase Available File Handles for MS-DOS-Based Programs in Windows Millennium Edition

  For additional information about the hotfix for Windows-based 16-bit programs that require more than 20 handles, click the article number below to view the article in the Microsoft Knowledge Base:

  274594 16-Bit Programs Cannot Open More Than 120 Files Simultaneously in Windows Me

• Setting: BUFFERS
  Default Value: 30
  User Configurable: No
  The BUFFERS setting is used by MS-DOS to provide limited buffering of file input/output (I/O) that is handled by MS-DOS real-mode drivers. Windows Me typically handles all I/O requests through the protected-mode input-output subsystem (Ios.vxd). This subsystem eliminates the need for MS-DOS BUFFERS support by providing a protected-mode cache, VCache. You cannot modify the BUFFERS setting because it is a fixed value in Windows Me. MS-DOS-based programs that require more than 30 buffers may not work correctly in Windows Me; however, Windows-based programs are not affected by the BUFFERS statement in most cases, even if the 30 existing MS-DOS buffers are not needed.
• Setting: STACKS
  Default Value: 0,0
  User Configurable: No
  The STACKS setting determines the number and size of the stack spaces that are created to handle interrupt handling in real mode. Because almost all of the device drivers that are used are written to run in protected mode, this value has no effect on the operation of existing MS-DOS-based programs.For additional information about the STACKS parameter, click the article number below to view the article in the Microsoft Knowledge Base:

  84300 How to Use the STACKS= Setting in the CONFIG.SYS File