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HOME TOPICS SEARCH ABOUT ME Microsoft wrote a good description of what the CONFIG.SYS file does in DOS 7 and Windows 95. Here it is in an easy-to-read form. |
technofile Al Fasoldt's reviews and commentaries, continuously available online since 1983 Microsoft's config.sys tips for DOS 7 and Windows 95---------------------------------------------------------------------- Microsoft Windows 95 README for MS-DOS Config.sys Commands August 1995 ---------------------------------------------------------------------- (c) Copyright Microsoft Corporation, 1995 This document provides complementary or late-breaking information to supplement the Microsoft Windows 95 documentation. ------------------------ How to Use This Document ------------------------ To view Config.txt on screen in Notepad, maximize the Notepad window. To print Config.txt, open it in Notepad or another word processor, then use the Print command on the File menu. In syntax lines, lowercase text signifies replaceable parameters and uppercase text must be typed as it appears. NOTE: The Msdosdrv.txt file contains more Help for MS-DOS commands. Also you can type the name of the command at the command prompt, followed by a slash and question mark (/?). For example: CHKDSK /? -------- CONTENTS ACCDATE BREAK BUFFERS/BUFFERSHIGH COUNTRY DEVICE DEVICEHIGH DOS DRIVPARM FCBS/FCBSHIGH FILES/FILESHIGH INSTALL/INSTALLHIGH LASTDRIVE/LASTDRIVEHIGH NUMLOCK REM SET SHELL STACKS/STACKSHIGH SWITCHES --------- ACCDATE ======= For each hard disk, specifies whether to record the date that files are last accessed. Last access dates are turned off for all drives when your computer is started in safe mode, and are not maintained for floppy disks by default. Syntax ACCDATE=drive1+|- [drive2+|-]... Parameters drive1, drive 2... Specifies the drive letter. +|- Specify a plus sign (+) to indicate that the last access date should be maintained for files on the drive. Specify a minus sign (-) to indicate that the last access date should not be maintained for files. BREAK ===== Sets or clears extended CTRL+C checking. You can use this command at the command prompt or in your CONFIG.SYS file. You can press CTRL+C to stop a program or an activity (file sorting, for example). Typically, MS-DOS checks for CTRL+C only while it reads from the keyboard or writes to the screen or a printer. If you set BREAK to ON, you extend CTRL+C checking to other functions, such as disk read and write operations. Syntax BREAK [ON|OFF] To display the current BREAK setting at the command prompt, use the following syntax: BREAK In your CONFIG.SYS file, use the following syntax: BREAK=ON|OFF Parameter ON|OFF Turns extended CTRL+C checking on or off. BUFFERS/BUFFERSHIGH =================== Allocates memory for a specified number of disk buffers when your system starts. Use the BUFFERSHIGH command to load the buffers in the upper memory area. You can use these commands only in your Config.sys file. Syntax BUFFERS=n[,m] BUFFERSHIGH=n[,m] Parameters n Specifies the number of disk buffers. The value of n must be in the range 1 through 99. The default is 30. m Specifies the number of buffers in the secondary buffer cache. The value of m must be in the range 0 through 8. The default is 0 (no secondary cache buffers). If you specify an invalid value for n or m, BUFFERs uses the default settings. COUNTRY ======== Enables MS-DOS to use country-specific conventions for displaying times, dates, and currency; for determining the order by which characters are sorted; and for determining which characters can be used in filenames. You can use this command only in your Config.sys file. The COUNTRY command configures MS-DOS to recognize the character set and punctuation conventions observed when using one of the supported languages. Syntax COUNTRY=xxx[,[yyy][,[drive:][path]filename]] Parameters xxx Specifies the country code. yyy Specifies the character set for the country. [drive:][path]filename Specifies the location and name of the file containing country information. DEVICE ====== Loads into memory the device driver you specify. You can use this command only in your Config.sys file. Syntax DEVICE=[drive:][path]filename [dd-parameters] Parameters [drive:][path]filename Specifies the location and name of the device driver you want to load. [dd-parameters] Specifies any command-line information required by the device driver. DEVICEHIGH ========== Loads a device driver you specify into the upper memory area. Loading a device driver into the upper memory area frees more bytes of conventional memory for other programs. If upper memory is not available, the DEVICEHIGH command functions just like the DEVICE command. You can use this command only in your Config.sys file. Syntax DEVICEHIGH [drive:][path]filename [dd-parameters] To specify the region(s) of memory into which to load the device driver, use the following syntax: DEVICEHIGH [[/L:region1[,minsize1][;region2[,minsize2] [/S]]= [drive:][path]filename [dd-parameters] Parameters [drive:][path]filename Specifies the location and name of the device driver you want to load into the upper memory area. dd-parameters Specifies any command-line information required by the device driver. Switches /L:region1[,minsize1][;region2[,minsize2]... Specifies one or more regions of memory into which to load the device driver. By default, MS-DOS loads the driver into the largest free upper memory block (UMB) and makes all other UMBs available for the driver's use. You can use the /L switch to load the device driver into a specific region of memory or to specify which region(s) the driver can use. To load the driver into the largest block in a specific region of upper memory, specify the region number after the /L switch. For example, to load the driver into the largest free block in region 4, you would type /L:4. (To list the free areas of memory, type MEM /F at the command prompt.) When loaded with the /L switch, a device driver can use only the specified memory region. Some device drivers use more than one area of memory; for those drivers, you can specify more than one region. (To find out how a particular device driver uses memory, issue the MEM /M command and specify the device-driver name as an argument.) To specify two or more regions, separate the block numbers with a semicolon (;). For example, to use blocks 2 and 3, you would type /L:2;3. Typically, MS-DOS loads a driver into a UMB in the specified region only if that region contains a UMB larger than the driver's load size (usually equal to the size of the executable program file). If the driver requires more memory while running than it does when loaded, you can use the minsize parameter to ensure that the driver will not be loaded into a UMB that is too small for it. If you specify a value for minsize, MS-DOS loads the driver into that region only if it contains a UMB that is larger than both the driver's load size and the minsize value. /S Shrinks the UMB to its minimum size while the driver is loading. Using this switch makes the most efficient use of memory. This switch is generally used only by the MemMaker program, which can analyze a device driver's memory use to determine whether the /S switch can safely be used when loading that driver. This switch can be used only in conjunction with the /L switch and affects only UMBs for which a minimum size was specified. DOS ==== Specifies that MS-DOS should maintain a link to the upper memory area, load part of itself into the high memory area (HMA), or both. You can use this command only in your Config.sys file. Syntax DOS=HIGH|LOW[,UMB|,NOUMB][,AUTO|,NOAUTO] DOS=[HIGH,|LOW,]UMB|NOUMB[,AUTO|,NOAUTO] DOS=[HIGH,|LOW,][UMB,|NOUMB,]AUTO|NOAUTO Parameters UMB|NOUMB Specifies whether MS-DOS should manage upper memory blocks (UMBs) created by a UMB provider such as Emm386.exe. The UMB parameter specifies that MS-DOS should manage UMBs, if they exist. The NOUMB parameter specifies that MS-DOS should not manage UMBs. The default setting is NOUMB. HIGH|LOW Specifies whether MS-DOS should attempt to load a part of itself into the HMA (HIGH) or keep all of MS-DOS in conventional memory (LOW). The default setting is LOW. AUTO|NOAUTO Specifies whether MS-DOS should automatically load Himem.sys, Ifshlp.sys, Dblbuff.sys, and Setver.exe device drivers if they are not explicitly loaded in your Config.sys file. The default setting, AUTO, automatically loads these device drivers. The AUTO setting also automatically uses the BUFFERSHIGH, FILESHIGH, FCBSHIGH, LASTDRIVEHIGH, and STACKSHIGH commands, whether the -HIGH form of the command was used or not. If you specify the NOAUTO parameter, you must explicitly load these device drivers and explicitly use the -HIGH form of the above commands in order to take advantage of them. DRIVPARM ======== Defines parameters for devices such as disk and tape drives when you start MS-DOS. You can use this command only in your Config.sys file. The DRIVPARM command modifies the parameters of an existing physical drive. It does not create a new logical drive. The settings specified in the DRIVPARM command override the driver definitions for any previous block device. Syntax DRIVPARM=/D:number [/C] [/F:factor] [/H:heads] [/I] [/N] [/S:sectors] [/T:tracks] Switches /D:number Specifies the physical drive number. Values for number must be in the range 0 through 255 (for example, drive number 0=drive A, 1=drive B, 2=drive C, and so on). /C Specifies that the drive can detect whether the drive door is closed. /F:factor Specifies the drive type. The following table shows the valid values for factor and a brief description of each. The default value is 2. 0 160K/180K or 320K/360K 1 1.2 megabyte (MB) 2 720K (3.5-inch disk) 5 Hard disk 6 Tape 7 1.44 MB (3.5-inch disk) 8 Read/write optical disk 9 2.88 MB (3.5-inch disk) /H:heads Specifies the maximum number of heads. Values for heads must be in the range 1 through 99. The default value depends on the value you specify for /F:factor. /I Specifies an electronically compatible 3.5-inch floppy disk drive. (Electronically compatible drives are installed on your computer and use your existing floppy disk drive controller.) Use the /I switch if your computer's ROM BIOS does not support 3.5-inch floppy disk drives. /N Specifies a nonremovable block device. /S:sectors Specifies the number of sectors per track that the block device supports. Values for sectors must be in the range 1 through 99. The default value depends on the value you specify for /F:factor. /T:tracks Specifies the number of tracks per side that the block device supports. The default value depends on the value you specify for /F:factor. FCBS, FCBSHIGH ============== Specifies the number of file control blocks (FCBs) that MS-DOS can have open at the same time. Use the FCBSHIGH command to load the FCBs in the upper memory area. You can use these commands only in your Config.sys file. A file control block is a data structure that stores information about a file. Syntax FCBS=x FCBSHIGH=x Parameter x Specifies the number of file control blocks that MS-DOS can have open at one time. Valid values for x are in the range 1 through 255. The default value is 4. FILES/FILESHIGH =============== Specifies the number of files that MS-DOS can access at one time. Use the FILESHIGH command to load the command in the upper memory area. You can use these commands only in your Config.sys file. Syntax FILES=x FILESHIGH=x Parameter x Specifies the number of files that MS-DOS can access at one time. Valid values for x are in the range 8 through 255. The default value is 8. INSTALL/INSTALLHIGH ==================== Loads a memory-resident program into memory when you start MS-DOS. Use the INSTALLHIGH command to load the memory-resident program into the upper memory area. You can use these commands only in your Config.sys file. Memory-resident programs stay in memory as long as your computer is on. They can be used even when other programs are active. You can use the INSTALL or INSTALLHIGH command to load MS-DOS memory-resident programs--for example, Fastopen, Keyb, Nlsfunc, and Share. Syntax INSTALL=[drive:][path]filename [command-parameters] INSTALLHIGH=[drive:][path]filename [command-parameters] Parameters [drive:][path]filename Specifies the location and name of the memory-resident program you want to run. command-parameters Specifies parameters for the program you specify for filename. LASTDRIVE/LASTDRIVEHIGH ======================= Specifies the maximum number of drives you can access. Use the LASTDRIVEHIGH command to load the LASTDRIVE data structures in the upper memory area. You can use these commands only in your Config.sys file. The value you specify represents the last valid drive that MS-DOS is to recognize. Syntax LASTDRIVE=x LASTDRIVEHIGH=x Parameter x Specifies a drive letter in the range A through Z. NUMLOCK ======== Specifies whether the NUM LOCK key is set to ON or OFF when your computer starts. You can use this command only in your Config.sys file. Syntax NUMLOCK=[ON|OFF] Parameters ON|OFF If set to ON, turns on the NUM LOCK key when MS-DOS displays the startup menu. If set to OFF, turns NUM LOCK off. REM === Enables you to include comments in a batch file or in your Config.sys file. The REM command is also useful for disabling commands. You can use a semicolon (;) instead of the REM command in your Config.sys file, but not in batch files. Syntax REM [string] Parameters string Specifies any string of characters -- the command you want to disable or the comment you want to include. SET === Displays, sets, or removes MS-DOS environment variables. You use environment variables to control the behavior of some batch files and programs and to control the way MS-DOS appears and works. The SET command is often used in the Autoexec.bat or Config.sys files to set environment variables each time you start MS-DOS. Syntax SET variable=[string] To display the current environment settings at the command prompt, use the following syntax: SET Parameters variable Specifies the variable you want to set or modify. string Specifies the string you want to associate with the specified variable. SHELL ===== Specifies the name and location of the command interpreter you want MS-DOS to use. You can use this command only in your Config.sys file. If you want to use your own command interpreter (instead of Command.com), you can specify its name by adding a SHELL command to your Config.sys file. Syntax SHELL=[[drive:]path]filename [parameters] Parameters [[drive:]path]filename Specifies the location and name of the command interpreter you want MS-DOS to use. parameters Specifies any command-line parameters or switches that can be used with the specified command interpreter. STACKS/STACKSHIGH ================= Supports the dynamic use of data stacks to handle hardware interrupts. Use the STACKSHIGH command to load the stacks in the upper memory area. You can use these commands only in your Config.sys file. Syntax STACKS=n,s STACKSHIGH=n,s Parameters n Specifies the number of stacks. Valid values for n are 0 and numbers in the range 8 through 64. s Specifies the size (in bytes) of each stack. Valid values for s are 0 and numbers in the range 32 through 512. SWITCHES ========= Specifies special options in MS-DOS. Use this command only in your Config.sys file. Syntax SWITCHES= /F /K /N /E[:n] Switches /F Skips the two-second delay after displaying the "Starting MS-DOS" message during startup. /K Forces an enhanced keyboard to behave like a conventional keyboard. /N Prevents you from using the F5 or F8 key to bypass startup commands. (SWITCHES /N does not prevent you from pressing CTRL+F5 or CTRL+F8 to bypass Drvspace.bin or Dblspace.bin; to prevent this, use the D**SPACE /SWITCHES command to add the SWITCHES /N setting to your D**space.ini file.) /E[:n] Used without the :n parameter, indicates that Io.sys should suppress the automatic relocation of EBIOS. (Automatic relocation of EBIOS increases the conventional memory available to MS-DOS-based programs.) Supressing automatic relocation results in less conventional memory available to MS-DOS-based programs. Use the /E switch with the n parameter to relocate N bytes of EBIOS to low memory, where n is the number of bytes to be relocated. The minimum value for n is 48 and the maximum value is 1024. The number specified is always rounded up to the next multiple of 16. |