Abstract
This chapter is targeted primarily at someone studying for the A+ Certification exam. You will learn how to describe the uses and commands of the Autoexec.bat and Config.sys files; optimize PC performance under MS-DOS, Windows 3.1, and Windows 95/98 through better memory management; and understand and use key configuration utilities under MS-DOS, Windows 3.1, and Windows 95/98. The chapter ends with a quiz and suggested activities.
Memory management has a dynamic impact on the overall speed and capability of the PC. No matter how much memory is installed, the lower area of memory (640K) is extremely important in the MS-DOS and Windows 3.x environment. Configuring the system to make best use of the memory available is critical.
Upon completion of this chapter, you will be able to
Describe the uses and commands of the Autoexec.bat and Config.sys files.
Optimize PC performance under MS-DOS, Windows 3.1, and Windows 95 through better memory management.
Understand and utilize key configuration utilities under MS-DOS, Windows 3.1, and Windows 95.
MS-DOS AND WINDOWS CONFIGURATION
Most of the configuration for MS-DOS is performed through the Config.sys and Autoexec.bat files. Config.sys loads all of the system devices and the Autoexec.bat runs programs automatically at boot time. The Config.sys file loads before Autoexec.bat.
The following sections examine Config.sys and Autoexec.bat and some typical MS-DOS commands and utilities.
Config.sys File
The Config.sys file loads device drivers and sets up memory management. The Config.sys file should look something like this:
Device=C:\DOS\Himem.sys
Device=C:\DOS\Emm386.exe
DOS=High, UMB
Files=40
Stacks=9256
Buffers=40
Lastdrive=M
Device=C:\MTM\Mtmcdai.sys /d:MTMIDE01
Table 10.1 explains the purpose of the lines in a typical Config.sys file. Many elements named in the table are described in greater detail below.
Memory Map
Several of the lines in the Config.sys file refer to drivers that manage various parts of memory. These memory locations can be difficult to track. Figure 10.1 shows a graphical map of memory. Please refer to it as we discuss the various aspects of the Config.sys file, below.
Himem.sys
Himem.sys is a driver that manages the first 64K of extended memory, which is also known as the high memory area (HMA). Latter versions of MS-DOS (5.0 and higher) use the HMA to reduce the use of conventional memory. If Himem.sys is used, it should be the first line loaded in the Config.sys. For more information about Himem.sys, type Help Himem.sys at the MS-DOS 6.22 command prompt.
Important: The load order of Himem.sys and Emm386.exe is significant. Himem.sys must be loaded first!
Emm386.exe
The Expanded Memory Manager (Emm386.exe) works to reduce the code stored in conventional memory by utilizing the upper memory area. The upper memory area is the area between 640K and 1024K (1 MB). Several devices load in this area, but some of these upper memory blocks (UMB) are unused. Emm386.exe uses them by loading devices and drivers that would normally load in conventional memory. For more information, type Help Emm386.exe at the MS-DOS 6.22 command prompt.
Autoexec.bat
The Autoexec.bat file loads after Config.sys during system boot. This file launches programs that help set the operating environment and load necessary terminate-and-stay resident (TSR) programs. TSR programs run in the background but provide you with added functionality. For example, Doskey.exe is a TSR that lets you recall previous commands by pressing the up arrow key.
Note: You can load Doskey.exe manually from the command prompt by typing Doskey. Then type a command and press the up arrow key to see that you can recall that command.
A sample Autoexec.bat file is listed below. C:\MTM\Mscdex.exe /D:MTMIDE01 /M:10
C:\DOS\Smartdrv.exe
@Echo Off
Prompt $p$g
Path: C:\Win3x; C:\DOS
Set Temp = C:\DOS
C:\DOS\Doskey
Note: Placing the letters REM in front of a line in the Config.sys or Autoexec.bat turns the lilne into a remark. The command is not processed by the system when REM is present.
Table 10.2 describes some of the typical commands in an Autoexec.bat file. The sections that follow the table describe some of these items in greater detail.
Mscdex.exe
The Mscdex.exe file uses the manufacturer’s CD-ROM driver to provide access to your CD-ROM through MS-DOS, Windows 3.x, and sometimes Windows 95 or Windows 98. Mscdex.exe loads in the Autoexec.bat and calls the CD-ROM driver that is loaded in the Config.sys. If the CD-ROM driver fails to properly load in the Config.sys, usually because it is the wrong driver or is corrupt, Mscdex.exe fails to load.
Smartdrv
Smartdrv provides extended memory disk caching. This program loads via the Autoexec.bat file. Smartdrv provides a type of caching called double-buffering, which provides compatibility for disk controllers that do not recognize 386 Enhanced mode. Essentially, Smartdrv improves system performance by placing selected data from the disk drive into memory.
For more information about Smartdrv, type Help Smartdrv at the MS-DOS 6.22 command prompt.
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