DOS Driver Software and TSRs
Most standard programs written for DOS did not necessarily need 640kb or more of memory. Instead, driver software and utilities referred to as Terminate and Stay Resident (TSR) programs could be used in addition to the standard DOS software. These drivers and utilities typically permanently used some conventional memory, reducing the total available for standard DOS programs.
Some very common DOS drivers and TSRs using conventional memory included:
- ANSI.SYS - support for color text and different text resolutions
- ASPIxDOS.SYS, ASPIDISK.SYS, ASPICD.SYS - all must be loaded for Adaptec SCSI drives and CDROMs to work
- DOSKEY.EXE - permits recall of previously typed DOS commands using up-arrow
- LSL.EXE, E100BODI.EXE (or other network driver), IPXODI.EXE, NETX.EXE - all must be loaded for Netware file server drive letter access
- MOUSE.EXE - support for mouse device in DOS programs
- MSCDEX.EXE - support for CDROM drive access and drive letter, used in combination with a separate manufacturer-specific driver. Needed in addition to above SCSI drivers for access to a SCSI CDROM device.
- SBCONFIG.EXE - support for Sound Blaster 16 audio device; a differently-named driver was used for various other sound cards, also occupying conventional memory.
- SMARTDRV.EXE - install drive cache to speed up disk reads and writes; although it could allocate several megabytes of memory beyond 640kb for the drive caching, it still needed a small portion of conventional memory to function.
As can be seen above, many of these drivers and TSRs could be considered practically essential to the full-featured operation of the system. But in many cases a choice had to be made by the computer user, to decide whether to be able to run certain standard DOS programs or have all their favorite drivers and TSRs loaded. Loading the entire list shown above is likely either impractical or impossible, if the user also wants to run a standard DOS program as well.
In some cases drivers or TSRs would have to be unloaded from memory to run certain programs, and then reloaded after running the program. For drivers that could not be unloaded, later versions of DOS included a startup menu capability to allow the computer user to select various groups of drivers and TSRs to load before running certain high-memory-usage standard DOS programs.
Read more about this topic: Conventional Memory
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