to initiate low level system utilities, such as the following: Virus scanners Disk caching software Mouse drivers Keyboard drivers CD drivers Miscellaneous other drivers Example In early versions of DOS, AUTOEXEC.BAT was by default very simple. The DATE and TIME commands were necessary as early PC and XT class machines did not have a battery backed-up real-time clock as default. @ECHO OFF CLS DATE TIME VER In non-US environments, the keyboard driver (like KEYB FR for the French keyboard) was also included. Later versions were often much expanded with numerous third-party device drivers. The following is a basic DOS 5 type AUTOEXEC.BAT configuration, consisting only of essential commands: @ECHO OFF PROMPT $P$G PATH C:\DOS;C:\WINDOWS SET TEMP=C:\TEMP SET BLASTER=A220 I7 D1 T2 LH SMARTDRV.EXE LH DOSKEY LH MOUSE.COM /Y This configuration sets common environment variables, loads a disk cache, places common directories into the default PATH, and initializes the DOS mouse / keyboard drivers. The PROMPT command sets the prompt to "C:\>" (when the working directory is the root of the C drive) instead of simply "C>" (the default prompt, indicating only the working drive and not the directory therein). In general, device drivers were loaded in CONFIG.SYS, and programs were loaded in the AUTOEXEC.BAT file. Some devices, such as mice, could be loaded either as a device driver in CONFIG.SYS, or as a TSR in AUTOEXEC.BAT, depending upon the manufacturer. In MS-DOS 6.0 and higher, a DOS boot menu is configurable. This can be of great help to users who wish to have optimized boot configurations for various programs, such as DOS games and Windows. @ECHO OFF PROMPT $P$G PATH C:\DOS;C:\WINDOWS SET TEMP=C:\TEMP SET BLASTER=A220 I7 D1 T2 GOTO %CONFIG% :WIN LH SMARTDRV.EXE LH MOUSE.COM /Y WIN GOTO END :XMS LH SMARTDRV.EXE LH DOSKEY GOTO END :END The GOTO %CONFIG% line informs DOS to look up menu entries that were defined within CONFIG.SYS. Then, these profiles are named here and configured with the desired specific drivers and utilities. At the desired end of each specific configuration, a GOTO command redirects DOS to the :END section. Lines after :END will be used by all profiles. Dual-booting DOS and Windows 9x When installing Windows 95 over a preexisting DOS/Windows install, CONFIG.SYS and AUTOEXEC.BAT are renamed to CONFIG.DOS and AUTOEXEC.DOS. This is intended to ease dual booting between Windows 9x and DOS. When booting into DOS, they are temporarily renamed CONFIG.SYS and AUTOEXEC.BAT.