Set MS-DOS 6.22 Temp Directory in AUTOEXEC.BAT

This article explains how to configure the temporary storage directory in MS-DOS 6.22 using the AUTOEXEC.BAT startup file. It covers the specific environment variables required, how to add them to the configuration, and standard practices for ensuring operating system utilities and third-party software have designated working space for temporary files.

In MS-DOS 6.22, the temporary storage directory is defined using the SET TEMP and SET TMP environment variable commands inside the AUTOEXEC.BAT file. While MS-DOS utilities primarily look for TEMP, many third-party programs and compilers look for TMP. Because of this, it is standard practice to define both variables to point to the exact same folder.

The Required Configuration Lines

To set the temporary directory, add the following lines to your AUTOEXEC.BAT file:

SET TEMP=C:\TEMP
SET TMP=C:\TEMP

If you prefer to place the directory inside the DOS directory, you can specify C:\DOS\TEMP instead.

Steps to Configure the Directory

  1. Create the Directory: MS-DOS will not automatically create the temporary folder if it does not exist. Create it at the command prompt by typing: 
    MD C:\TEMP
  2. Edit AUTOEXEC.BAT: Open the startup file using the MS-DOS Editor: 
    EDIT C:\AUTOEXEC.BAT
  3. Add the Commands: Place SET TEMP=C:\TEMP and SET TMP=C:\TEMP on their own lines, typically near the top of the file alongside other SET commands (such as PATH).
  4. Save and Exit: Press Alt + F, select Save, and then exit the editor.
  5. Apply Changes: Restart your computer or run C:\AUTOEXEC.BAT directly from the command prompt to load the new environment variables into memory.

Using a RAM Drive for Faster Performance

In MS-DOS 6.22, temporary file operations can be significantly accelerated by redirecting the temporary path to a virtual RAM drive created with RAMDRIVE.SYS in CONFIG.SYS.

If RAMDRIVE.SYS assigns drive letter D: to your RAM disk, you can set the temporary variables in AUTOEXEC.BAT as follows:

MD D:\TEMP
SET TEMP=D:\TEMP
SET TMP=D:\TEMP

This configuration prevents unnecessary disk read/write cycles on physical drives and speeds up utilities like MS-DOS Editor, defragmentation tools, and file archivers.