Each hardware component of your computer is called a device. Your computer's keyboard, mouse, display, printer, disk drives, and memory boards are all devices.
Each device has its own characteristics that can be customized.
DOS uses a special program called a device driver to control each device. For example, DOS uses a built-in device driver to control how information is read to and from a diskette drive. DOS has built-in device drivers for your keyboard, display, hard and diskette drives, and communication ports. Because these device drivers are built in, you do not have to do anything special to use them. You can
customize certain features of these devices by using CONFIG.SYS commands. For a list of these commands, see "CONFIG.SYS Commands" on page 30.
Other devices, such as memory boards or a mouse, have device drivers that are not built into DOS. Such a device driver is called an instal/able device driver because you install it by adding a command to your CONFIG.SYS file. Many hardware devices come with their own device drivers. For example, DOS comes with a device driver called HIMEM.SYS. Several other installable device drivers are included with DOS.
To use an installable device driver, add a DEVICE command for that driver to your CONFIG.SYS file. When DOS starts, it loads the device driver into memory. For example, to load the HIMEM.SYS device driver from the C:\DOS directory, you would add a command like the following to your CONFIG.SYS file:
device=c:\dos\himem.sys
When DOS reads this command, it loads the HIMEM.SYS device driver into memory. The HIMEM.SYS device driver remains in memory and manages extended memory.
Note: Many hardware devices come with installation programs that automatically add the necessary commands to your CONFIG.SYS file.
DOS comes with the following installable device drivers.
Supports American National Standards Institute (ANSI) terminal emulation.
Replaces the default DOS clock so that any request for the current date and time accesses CMOSCLK.SYS instead of the DOS system clock. Normally used only if your current DOS system clock is not keeping the correct date.
Supports code-page switching for displays.
Creates a logical drive that you can use to refer to a physical disk driver and specifies parameters for a drive not supported by your computer's ROM BIOS.
Saves and restores the display when a graphics program is used with an EGA monitor.
Simulates expanded memory and provides access to the upper memory area on a computer with at least an 80386 processor and extended memory.
Manages the use of extended memory on a computer install the INTERLNK.EXE device driver before you can use the INTERLNK and INTERSVR commands.
Provides virtual block device driver support for PCMCIA AT A fixed disk cards if they are formatted with a FAT-compatible disk structure.
Loads PCMCIA Card Services support. Can be loaded either as a terminate-and-stay-resident program from the DOS command prompt or as a device driver when included in the CONFIG.SYS file .
•• Hercules is a trademark of Hercules Computer Technology.
eGA, EGA, and VGA are trademarks of the IBM Corporation.
Driver
Emulates diskette drives from PCMCIA cards. Can be loaded either as a terminate-and-stay-resident program from the DOS command prompt or as a device driver when included in the CONFIG.SYS file.
Installs one or more Memory Technology Drivers (MTDs) so that PCMCIA cards with different memory technologies can be loaded either as a
terminate-and-stay-resident program from the DOS command prompt or as a device driver when included in the CONFIG.SYS file.
Installs one or more Super Client Drivers (SCDs) so that PCMCIA cards with different devices, such as fax machines or modems, can be supported. Can be loaded either as a terminate-and-stay-resident program from the DOS command prompt or as a device driver when included in the CONFIG.SYS file.
Provides the PenDOS application programming interface (API) for PenDOS applications.
Provides the ability to reduce the consumption of power when your applications and devices are idle.
Supports code-page switching for printers.
Simulates a hard disk drive by creating a virtual disk drive in your system's random access memory (RAM).
Increases your computer's conventional memory and makes using EMM386.EXE less complex.
Automatically analyzes your computer's current configuration and then reconfigures it automatically to load terminate-and-stay-resident programs and device drivers into upper memory blocks. This eliminates the need to manually edit your CONFIG.SYS or
AUTOEXEC.BAT files because it maintains a data file called RAMBOOST.INI to track the programs and device drivers that need to be loaded into upper memory.
Loads the DOS version table into memory.
Driver Upper Memory Blocks (UMBs) that are used for loading programs with the LOADHIGH command if a CGA*, EGA*, or VGA* adapter is also present. It provides approximately 4K of extra memory.
Maps the video memory of a color adapter as Upper Memory Blocks (UMBs) that are used for loading programs with the LOADHIGH command if a CGA, EGA, or VGA adapter is also present. It provides approximately 16K of extra memory.
Maps the video memory of a Hercules** adapter as Upper Memory Blocks (UMBs) that are used for loading programs with the LOADHIGH command if a Hercules graphics adapter or a Hercules Graphics Adapter Plus is also present. It provides approximately 60K of extra because some device drivers enable devices that are then used by other drivers.
For example, the HIMEM.SYS extended-memory driver must be started before any drivers that use extended memory.
The order in which device drivers should appear in your CONFIG.SYS file is as follows:
1. HIMEM.SYS if your system has extended memory.
2. Your expanded-memory manager if your system has an expanded-memory board.
3. EMM386.EXE if your system is an 80386 or higher processor with extended memory. If your CONFIG.SYS file includes both an expanded-memory
manager and EMM386, the EMM386 command line should include the noems switch.
EMM386 uses extended memory to simulate expanded memory on systems that do not have expanded memory. EMM386 can also provide access to the upper memory area. For more information, see Chapter 10, "Making More Memory Available" on page 163.
4. Any other device drivers.
Note: This list is intended to show only the correct order for device drivers. It is not intended to be a list of the commands that your CONFIG.SYS file should contain. The contents of your system's CONFIG.SYS file depends on the type of system, the amount or type of memory, the hardware configuration, and the applications you use.