COMMAND
`
`COMMAND
`Command Processor
`
`1.0 and later
`
`External
`
`Purpose
`Loads a secondary copy of the MS-DOS default command processor.
`Syntax
`COMMAND [drive:Hpath] [device] [/E:n] [/P] [/C string]
`
`where:
`
`path
`
`device
`
`is the name of the directory to be searched for COMMAND. COM when the
`transient portion needs to be reloaded; a drive letter can be included with ver(cid:173)
`sions 2.0 and later.
`is the name of a character device to be used instead of CON for the command
`processor's input and output (versions 2.0 and later).
`is the initial size, in bytes, of the command processor's environment block
`(160-32768, default= 160) (version 3.2).
`fixes the newly loaded command processor permanently in memory (versions
`2.0 and later).
`/C string causes the command processor to behave as a transient program and execute
`the command or program specified by string(versions 2.0 and later).
`
`/E: n
`
`/P
`
`Description
`The command processor is the module of the operating system that is responsible for
`issuing prompts to the user, interpreting commands, loading and executing transient appli(cid:173)
`cation programs, and interpreting batch files. The file COMMAND. COM contains the
`MS-DOS default command processor, or shell. It is ordinarily loaded from the root direc(cid:173)
`tory of the system disk when the system is turned on or restarted, unless the SHELL com(cid:173)
`mand is used in the CONFIG.SYS file to specify another command processor or an
`alternate location for COMMAND. COM.
`
`With versions l.x, COMMAND. COM is invoked by the COMMAND command in re(cid:173)
`sponse to a shell prompt or within a batch file. A second copy of the resident portion of
`COMMAND. COM is loaded and the memory occupied by the original resident portion is
`lost. The second copy of the transient portion simply overlays the original transient por(cid:173)
`tion. (Versions l.x of COMMAND support no switches or other parameters and any speci(cid:173)
`fied in the command line are ignored.) With versions 2.0 and later, the new copy of
`COMMAND. COM is loaded in addition to the parent command processor and serves ·
`as a secondary command processor.
`
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`

`
`COMMAND
`
`The path parameter specifies the location of the COMMAND. COM file that is used to
`reload the transient part of the command processor if it is overlaid by application pro(cid:173)
`grams. If absent, path defaults to the root directory of the system (startup) disk.
`
`The device parameter allows a character device other than CON to be used by the com(cid:173)
`mand processor for input and output. For example, use of AUX as the device parameter
`allows a personal computer to be controlled from a terminal attached to a serial port,
`instead of from the usual built-in keyboard and memory-mapped video display.
`
`The secondary copy of COMMAND. COM ordinarily remains in memory and serves as the
`active command processor until an EXIT command is entered. If a /P switch is used with
`the COMMAND command, the new copy of COMMAND.COM is fixed in memory and the
`EXIT command is disabled. In such cases, the memory occupied by previously loaded
`copies of COMMAND. COM is simply lost.
`
`The /E: n switch controls the size of the environment block initially allocated for the
`command processor. The default size of the block is 160 bytes, but the /E: n switch allows
`the initial allocation to be as large as 32768 bytes. This switch is frequently used when
`COMMAND. COM is included in the SHELL command in the CONFIG.SYS file.
`
`When the /C string switch is included in the command line, followed by a string desig(cid:173)
`nating a command or program name, the new copy of COMMAND. COM carries out the
`operation specified by string and then exits, returning control to its parent command pro(cid:173)
`cessor or other program. This option allows a batch file to invoke another batch file and
`then resume its own execution. (If a batch file names another batch file directly without
`using COMMAND /C string as an intermediary, the first batch file is terminated.) Note
`that when the /C string switch is used in combination with other switches, it must be
`the last switch in the command line.
`
`A secondary copy of COMMAND. COM always inherits a copy of the environment of
`the command processor or other program that loaded it. Changes made to the new
`COMMAND. COM's environment with a SET, PROMPT, or PATH command do not affect
`the environment of any previously loaded program or command processor.
`Examples
`To execute the batch file MENU2.BAT from the batch file MENUl.BAT and then resume
`execution of MENUl.BAT, include the following line in MENUl.BAT:
`
`COMMAND /C MENU2
`
`To cause COMMAND. COM to be loaded from the directory \SYSTEM on drive C rather
`than from the root directory and to allocate an initial environment block of 1024 bytes,
`include the following line in the CONFIG.SYS file:
`
`SHELL=C:\SYSTEM\COMMAND.COM C:\SYSTEM /P /E:1024
`
`Section Ill: User Commands
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`

`
`COMMAND
`
`Messages
`Bad or missing command interpreter
`The file COMMAND. COM is not present in the root directory of the system disk and no
`SHELL command is present to specify an alternate command processor file or location, or
`the location specified for COMMAND. COM in a SHELL command is not correct. This mes(cid:173)
`sage may also be seen if COMMAND. COM is moved from its original location after the
`system is booted.
`""
`Invalid device
`The character device specified in the command line is not valid or does not exist.
`Invalid environment size specified
`The value supplied with the /E: n switch was less than 160 bytes or greater than 32768
`bytes.
`
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`

`
`COMP
`Compare Files
`
`COMP
`
`IBM
`
`External
`
`Purpose
`Compares two files or sets of files. This command is available only with PC-DOS.
`Syntax
`COMP [primary] [secondary]
`
`where:
`
`primary
`
`secondary
`
`is the name of the file to be compared against and can be preceded by a
`drive arid/or path; wildcard characters are permitted in the filename.
`is the name of the file to be compared with primary and can be preceded
`by a drive and/or path; wildcard characters are permitted in the filename.
`
`Description
`The COMP command compares one file or set of files with another. As each pair of files is
`compared, the program reports whether the files are identical, different in size, or the
`same size but different in content.
`
`The primary and secondary parameters can be any combination of drive,· path, and file(cid:173)
`name, optionally including wildcards to allow sets of files to be compared. (With versions
`l.x, using wildcards does not cause multiple file comparisons- only the first secondary
`file whose name matches the first primary filename is compared.) The primary parameter
`generally designates the specific files to be compared; the secondary parameter is usually
`only a drive and/or path, except when the files being compared have different names or
`extensions.
`
`If both primary and secondary are omitted from the command line, the COMP program
`prompts for them interactively. If primary is given as a drive or path only, COMP assumes
`*·*to be the primary file. If secondary is given as a drive or path only, COMP compares all
`files on that drive or path whose filenames match those of the primary files.
`
`The COMP command is included only with PC-DOS. MS-DOS versions 2.0 and later
`provide a similar function in the FC command, which also displays the differences be(cid:173)
`tween files.
`Examples
`To compare the file MYFILE.DAT on the disk in drive A with the file LEDGER.DAT on the
`disk in drive B, type
`
`c>COMP A:MYFILE.DAT B:LEDGER.DAT <Enter>
`
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`

`
`COMP
`
`To compare all the files in the current directory of the disk in drive A with the
`corresponding files in the current directory of the disk in drive D, type
`
`C>COMP A:*.* D: <Enter>
`
`To compare all the files with the extension .ASM in the directory C: \SOURCE with the
`corresponding files with extension .BAK on the disk in drive B, type
`
`C>COMP C:\SOURCE\*.ASM B:*.BAK <Enter>
`Messages
`10 mismatches- ending compare
`The primary and secondary files are the same size but have more than 10 internal differ(cid:173)
`ences. The compare operation on this pair of files is aborted and COMP proceeds to the
`next pair of files, if any.
`
`filename and .filename
`This informational message shows the full filenames of the two files currently being
`compared.
`
`Access Denied
`An attempt was made to compare a locked file.
`
`Cannot compare file to itself
`An attempt was made to compare a file with itself.
`
`Compare error at OFFSET nn
`Filel=nn
`File2 =nn
`This informational message itemizes the first 10 differences in data between the two files
`being compared (if the files are the same size), displaying the file offset and the differing
`bytes from each file as hexadecimal values.
`
`Compare more files (YIN)?
`After all specified pairs of files have been compared, the COMP program allows the entry
`of another pair of file specifications. Respond with Y or press Enter to continue; respond
`with N to terminate the COMP program.
`
`Enter 2nd file name or drive id
`If the secondary filename was not specified in the COMP command, this message prompts
`the user to enter it (or a path, if the secondary file has the same name as the primary file).
`
`Enter primary file name
`If no parameter was entered after COMP, this message prompts the user to enter the pri(cid:173)
`mary filename. If a drive or path is specified, COMP assumes •.• for the primary filename.
`
`EOF mark not found
`The last byte at the logical end of the file was not a Control-Z character 0Z, or lAH). This
`message is commonly seen during comparison of two files that are not ASCII text files,
`such as executable program files.
`
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`

`
`COMP
`
`. Files compare OK
`The files being compared were the same length and contained identical data.
`
`File not found
`The specified filename was invalid or the file does not exist.
`
`Files are different sizes
`The two files being compared have different sizes recorded in the directory. No com(cid:173)
`parison on the data within the files is attempted.
`
`File sharing conflict
`COMP is unable to compare the two current files because one of the files is in use by
`another process.
`
`Incorrect DOS version
`The version of COMP is not compatible with the version of PC-DOS that is running.
`
`Insufficient memory
`The available system memory is insufficient to run the COMP program.
`
`Invalid drive specification
`The drive specification in primary or secondary is invalid or does not exist.
`
`Invalid path
`The path or directory in primary or secondary is invalid or does not exist.
`
`Too many files open
`No more system file handles are available. Increase the value of the FILES command in the
`CONFIG.SYS file and restart the system.
`
`Section III: User Commands
`
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`

`
`CONFIG.SYS
`
`CONFIG.SYS
`System Configuration File
`
`2.0 and later
`
`Purpose
`Allows the user to configure the operating system.
`Description
`The CONFIG.SYS file is an ASCII text file that MS-DOS processes during initialization
`(when the system is turned on or restarted). It allows the user to configure certain aspects
`of the operating system, such as the number of internal disk buffers allocated, the number
`of files that can be open at one time, the formats for date and currency, and the name and
`location of the executable file containing the command processor. CONFIG.SYS can also
`contain commands that extend the system with installable device drivers for terminal
`emulation, virtual disks or RAMdisks, extended or expanded memory, and other special
`peripheral devices.
`
`The CONFIG.SYS file can be created or modified with EDLIN or with any other editor or
`word processor that can produce ordinary ASCII text files (nondocument files) and save
`them to disk. The CONFIG.SYS file must be in the root directory of the disk that is used to
`start the operating system in order for it to be processed during system initialization.
`When changes are made to the CONFIG.SYS file, they do not take effect until the system
`is restarted.
`
`Commands in the CONFIG.SYS file take the form
`
`command[=]value
`
`(Note that the equal sign is optional; any other valid MS-DOS separator [semicolon, tab, or
`space] can be used instead.) The commands supported are
`
`Comniand
`
`Action
`
`BREAK
`BUFFERS
`
`COUNTRY
`DEVICE
`DRIVPARM
`
`FCBS
`
`Controls extended checking for Control-C.
`Specifies the number of internal disk-sector buffers available for use by
`MS-DOS when reading from or writing to a disk.
`Controls date, time, and currency formatting.
`Specifies the filename of an installable device driver.
`Redefines the default characteristics of the resident MS-DOS block
`device(s) (version 3.2).
`Specifies the maximum number of simultaneously open file control blocks
`(versions 3.0 and later).
`
`(more)
`
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`

`
`CONFIG.SYS
`
`!
`
`I
`
`.Command Action
`
`FILES
`
`LASTDRIVE
`SHELL
`
`STACKS
`
`. Specifies the maximum number of simultaneously open files controlled by
`handles.
`Sets the highest valid drive letter (versions 3.0 and later).
`Specifies the filename (and optionally the drive and/or path) of the system
`command processor.
`Sets the number and size of stack frames for the system.
`
`Each of these commands is discussed in detail on the following pages.
`Message
`Unrecognized command in CONFIG.SYS
`A command in the CONFIG.SYS file was misspelled, an invalid parameter was used, or a
`command was included that is not compatible with the version of MS-DOS that is running.
`Correct the CONFIG.SYS file and restart the system.
`
`Section Ill: User Commands
`
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`

`
`CONFIG.SYS: BREAK
`
`CONFIG.SYS: BREAK
`Configure Control-C Checking
`
`2.0 and later
`
`Purpose
`
`Sets or clears MS-DOS's internal flag for Control-C checking.
`Syntax
`
`BREAK=ON :OFF
`Description
`Pressing Ctrl-C or Ctrl-Break while a program is running ordinarily terminates the pro(cid:173)
`gram, unless the program itself contains instructions that disable MS-DOS's Control-C
`handling. As a rule, MS-DOS checks the keyboard fora Control-C only when a character is
`read from or written to a character device (keyboard, screen, printer, or auxiliary port).
`Therefore, if a program executes for long periods without performing such character 1/0,
`detection of the user's entry of a Control-C may be delayed. The BREAK=ON command
`causes MS-DOS to also check the keyboard for a Control-C at the time of each system call
`(which slows the system somewhat); the BREAK=OFF command disables such extended
`Control-C checking. The default setting for BREAK is off.
`
`Extended Control-C checking can also be enabled or disabled at the command prompt
`with the interactive form of the BREAK command whenever the system is running.
`Example
`
`To enable extended Control-C checking during MS-DOS disk operations, insert the line
`
`BREAK=ON
`
`into the CONFIG.SYS file and restart the system.
`Message
`Unrecognized command in CONFIG.SYS
`The setting supplied for the BREAK command was not ON or OFF. Correct the
`CONFIG.SYS file and restart the system.
`
`790
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`
`ZTE (USA) 1007, Page 800
`
`

`
`CONFIG.SYS: BUFFERS
`
`2.0 and later
`
`CONFIG.SYS: BUFFERS
`Configure Internal Disk Buffers
`
`Purpose
`Sets the number of MS-DOS's internal disk buffers.
`Syntax
`
`BUFFERS=nn
`
`where:
`
`nn
`
`is the number of buffers (1-99, default = 2; default = 3 for IBM PC/AT and
`compatibles).
`
`Description
`MS-DOS maintains a set of internal buffers (sometimes referred to as a disk cache) in
`which it keeps copies of the sectors most recently read from or written to the disk. When(cid:173)
`ever a program requests a disk read, MS-DOS first searches the disk buffers to determine
`whether a copy of the disk sector containing the required data is already present in RAM.
`If the sector is found, the actual disk access is bypassed. This technique can significantly
`improve the overall performance of the disk operating system.
`
`By using the BUFFERS command in the CONFIG.SYS file, the user can control the number
`of buffers in MS-DOS's disk cache. The default number of buffers is 2 for an IBM PC,
`PC/XT, or compatible and 3 for an IBM PC/AT or compatible. The optimum number of
`buffers varies, depending in part on the characteristics and types of the system disk drives,
`the types of application programs used on the system, the number and levels of subdirec(cid:173)
`tories in the file structure, and the amount of RAM in the system.
`
`If the system has only floppy-disk drives, the default setting of 2 buffers is sufficient. If the
`system includes a fixed disk, increasing the number of buffers to 10 or so typically speeds
`up overall system operation. Configuring the system for too many buffers, however, can
`actually degrade the performance of the system.
`
`Increases in the number of buffers should be tailored to the type of application most fre(cid:173)
`quently used. For example, allocation of extra disk buffers will not improve the perfor(cid:173)
`mance of programs that use primarily sequential file access but may considerably enhance
`the execution times of programs that perform random access on a relatively small number
`of disk records (such as the index for a database file). In addition, if the system has many
`subdirectories organized in several levels, increasing the number of buffers can signifi(cid:173)
`cantly increase the speed of disk operations.
`
`The ideal number of buffers for a given system is difficult to predict because of the interac(cid:173)
`tions between the access time of the disk, the speed of the central processing unit, and the
`
`Section Ill: User Commands
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`

`
`CONFIG.SYS: BUFFERS
`
`RAM requirements and disk access behavior of the mix of application programs. However,
`a reasonably optimal number of buffers can be quickly estimated experimentally by in(cid:173)
`creasing the number of buffers in increments of five or so, restarting the system, perform(cid:173)
`ing some simple timing tests on the most frequently used application programs, and
`observing at what number of buffers system performance begins to degrade.
`Example
`To allocate 20 internal disk buffers, insert tbe line
`
`BUFFERS=20
`
`into the CONFIG.SYS file and restart the system.
`Message
`Unrecognized command in CONFIG.SYS
`The value supplied for the BUFFERS command was not a number in the range 1 through
`99.
`
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`
`

`
`CONFIG.SYS: COUNTRY
`Set Country Code
`
`CONFIG.SYS: COUNTRY
`
`2.1 and later
`
`Purpose
`Configures MS-DOS's internationalization support for a specific country.
`Syntax
`
`COUNTRY=nnn
`
`where:
`
`nnn
`
`is the international telephone dialing prefix for the country (001-999, default =
`001):
`
`Australia
`Belgium
`Denmark
`Finland
`France
`Israel
`Italy
`Netherlands
`Norway
`Spain
`Sweden
`Switzerland
`United Kingdom
`USA
`West Germany
`
`061
`032
`045
`358
`033
`972
`039
`031
`047
`034
`046
`041
`044
`001
`049
`
`Note: In versions 2.x (except 2.0), nnn is 01 through 99. Individual computer manufactur(cid:173)
`ers determine the specific codes supported by their versions of MS-DOS.
`Description
`The COUNTRY command enables the user to tailor MS-DOS's date, time, and currency
`displays for a specific country. This capability, termed internationalization support, is
`achieved through use of a country code that controls the contents of the table MS-DOS
`uses to format these displays (including numeric separators). (The internationalization
`table is made available to application programs through Interrupt 21H Function 38H.)
`Beginning with version 3.0, PC-DOS also supports the COUNTRY command.
`
`Section Ill: User Commands
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`
`

`
`CONFIG.SYS: COUNTRY
`
`Example
`In West Germany, the format for the date is dd.mm.yy. To configure MS-DOS to use this
`date format, insert the line
`
`COUNTRY=049
`
`into the CONFIG.SYS file and restart the system.
`Message
`Invalid country code
`The specified country code is not supported by the version of MS-DOS that is running.
`
`794
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`
`ZTE (USA) 1007, Page 804
`
`

`
`CONFIG.SYS: DEVICE
`
`2.0 and later
`
`CONFIG.SYS: DEVICE
`Install Device Driver
`
`Purpose
`
`Loads and links an installable device driver into the operating system during initialization.
`Syntax
`DEVICE=[drive:][pathlfilename [options]
`
`where:
`
`filename
`
`options
`
`is the name of the device-driver file, optionally preceded by a drive and/or
`path.
`specifies any switches or other parameters needed by the device driver; the
`DEVICE command itself has no switches.
`
`Description
`Device drivers are the modules of the operating system that control the interface between
`the operating system and peripheral devices such as disk drives, magnetic-tape drives,
`CRT terminals, and printers.
`
`As supplied, MS-DOS already contains device drivers for the keyboard, video display, serial
`port, printer, real-time clock, and disk devices. Device drivers for additional peripheral
`devices can be linked into the operating system by adding a DEVICE command to the
`CONFIG.SYS file, placing the file containing the device driver on the system startup disk
`(or at the location specified by the drive: and/or path parameter), and restarting the
`computer.
`
`If a drive other than the one containing the system disk is named as the location of the
`device driver, that drive must either be accessible via the system's default disk driver or be
`a drive configured with a previous DEVICE command.
`
`Most OEM implementations of version 3.2 provide three installable device drivers:
`ANSI.SYS, which allows the video display and keyboard to be controlled by ANSI standard
`escape sequences; DRIVER.SYS, which supports external disk drives; and RAMDRIVE.SYS
`(VDISK.SYS with PC-DOS), which uses a portion of the machine's RAM to emulate a disk
`drive. See USER COMMANDS: ANSI.sYs; DRIVER.sYs; RAMDRIVE.SYS; VDISK.SYS.
`
`Many manufacturers of add-on products for MS-DOS machines (such as network interfaces
`or Lotus/Intel/Microsoft Expanded Memory boards) also supply installable device drivers
`for use with their hardware. For information concerning these drivers, see the product
`manufacturer's user's manual.
`
`Section III: User Commands
`
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`

`
`CONFIG.SYS: DEVICE
`
`Examples
`To load the ANSI standard console driver, insert the line
`
`DEVICE=ANSI.SYS
`
`into the CONFIG.SYS file, place the file ANSI.SYS in the root directory of the system disk,
`and restart the system.
`To load the RAMDRIVE.SYS driver located !V the \DRIVERS directory on the disk in drive
`A, configt!ring it for 1024 KB in extended memory, insert the line
`
`DEVICE=A:\DRIVERS\RAMDRIVE.SYS 1024 /E
`
`into the CONFIG.SYS file and restart the system.
`Messages
`Bad or missing filename
`The filename specified in the DEVICE command is invalid or does not exist or the file
`does not contain a valid MS-DOS installable device driver.
`
`Sector size too large in file filename
`The specified installable device driver uses a sector size that is larger than the sector size
`used by any of the system's default disk drivers. Such a driver cannot be used because
`MS-DOS's internal disk buffers will not be large enough to hold a sector read from the
`device.
`
`796
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`
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`
`

`
`CONFIG.SYS: DRIVPARM
`
`CONFIG.SYS: DRIVPARM
`Set Block-Device Parameters
`
`3.2
`
`Purpose
`Alters the system's list of characteristics for an existing block device.
`Syntax
`DRIVPARM=/D:n[/C] [/F:n] [/H:n] [/N] [/S:n] [/T:n]
`
`where:
`
`/D: n
`
`!C
`/F: n
`
`is the drive number (0-255; 0 =A, 1 = B, etc.) and must always be the first
`switch in the command line.
`indicates that the device provides door-lock-status support.
`is a form-factor index from the following table (default= 2 if the DRIVPARM
`command is present but this switch is omitted):
`
`320 KB or 360 KB
`0
`1 1.2MB
`2
`720KB
`3
`8-inch single-density floppy disk
`4
`8-inch double-density floppy disk
`5 Fixed disk
`6 Tapedrive
`7 Other
`
`/H: n
`IN
`IS: n
`IT: n
`
`is the number of read/write heads (1-99).
`indicates that the block device is not removable.
`is the number of sectors per track (1-99).
`is the number of tracks per side (1-999).
`
`Note: The DRIVPARM command must not be used to specify device characteristics that
`the device driver is not capable of supporting.
`Description
`Whenever the device driver for a block device such as a disk drive or magnetic-tape drive
`performs input or output, it refers to an internal table of characteristics for the device that
`allows it to convert logical addresses to physical addresses. The DRIVPARM command
`modifies the default MS-DOS values in the table of characteristics for a particular block
`device during system initialization (when the computer is turned on or restarted). Multiple
`DRIVPARM commands, each modifying the characteristics of a different block device, can
`be included in the same CONFIG.SYS file. Any characteristics not specifically altered in
`
`Section III: User Commands
`
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`ZTE (USA) 1007, Page 807
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`

`
`CONFIG.SYS: DRIVPARM
`
`the DRIVPARM command for a particular device retain their original values, except for
`/F: n, which defaults to 2.
`
`DRIVPARM commands that alter the characteristics for block devices controlled by install(cid:173)
`able device drivers must follow the DEVICE command that loads the device driver itself.
`Example
`Assume that drive B is a floppy-disk drive originally configured for 40 tracks with 8 sectors
`per track. To reconfigure the drive to read or write 80 tracks of 9 sectors each, insert the
`line
`
`DRIVPARM=/D:1 /S:9 /T:SO
`
`into the CONFIG.SYS file and restart the system. For this command to be valid the drive
`must be capable of supporting these parameters.
`Message
`Unrecognized command in CONFIG.SYS
`An invalid parameter was specified in a DRIVPARM command.
`
`798
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`
`ZTE (USA) 1007, Page 808
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`
`CONFIG.SYS: PCBS
`
`CONFIG.SYS: FCBS
`Set Maximum Open Files Using File Control Blocks (FCBs)
`
`3.0 and later
`
`Purpose
`
`Configures the maximum number of files that can be open concurrently using file control
`blocks (FCBs). This command has no practical effect unless either the file-sharing support
`module SHARE.EXE or networking support has been loaded.
`Syntax
`
`FCBS=m,p
`
`where:
`
`m
`
`is the maximum number of files that can be open concurrently using FCBs (1- 255,
`default = 4).
`is the number of files opened with FCBs that are protected against automatic closure
`(0-m, default= 0).
`Description
`
`p
`
`MS-DOS supports two methods of file access: file control blocks and file handles. A file
`control block is a data structure that stores information about an open file. It resides inside
`an application program's memory space and is accessed by both MS-DOS and the applica(cid:173)
`tion. (See USER COMMANDS: coNFIG.sYs: FILEs for information on file handles.)
`
`In a network environment, a large number of active FCBs or improper use of FCBs by
`an application can seriously degrade the performance of the network as a whole. Conse(cid:173)
`quently, MS-DOS versions 3.0 and later provide the FCBS command to enable the user to
`limit the number of files that can be open concurrently using FCBs if either the file-sharing
`support module SHARE.EXE (see USER COMMANDS: SHARE) or rietwork support has
`been loaded. If an application program attempts to exceed the specified number of files,
`MS-DOS closes the file with the least recently used FCB.
`The p parameter in the FCBS command line allows the user to protect files from unilateral
`closure by MS-DOS. The value of pis the number of files, counting from the first file
`opened using an FCB, that cannot be closed automatically.
`
`If the current value of FCBS is 4, 0 (the default) when the file-sharing module SHARE.EXE
`or network support is loaded, MS-DOS automatically increases the maximum number of
`files that can be open concurrently to 16 and the number of files protected against automa(cid:173)
`tic closure to 8. (When multiple FCBs refer to the same file, the file is counted only once.)
`
`Section Ill: User Commands
`
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`ZTE (USA) 1007, Page 809
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`

`
`CONFIG.SYS: PCBS
`
`Examples
`
`To set the maximum number of files that can be concurrently open using FCBs to 10 and
`protect none of the FCB-opened files against automatic closure by MS-DOS, insert the line
`
`FCBS=10,0
`
`into the CONFIG.SYS file and restart the system.
`
`To set the maximum number of files that can be concurrently open using FCBs to 8 but
`protect the first 4 FCB-opened files against automatic closure by MS-DOS, insert the line
`
`FCBS=8,4
`
`into the CONFIG.SYS file and restart the system.
`Message
`Unrecognized command in CONFIG.SYS
`An invalid number was specified as one of the parameters in the FCBS command.
`
`800
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`The MS-DOS Encyclopedia
`
`ZTE (USA) 1007, Page 810
`
`

`
`CONFIG.SYS: FILES
`Set Maximum Open Files Using Handles
`
`CONFIG.SYS: FILES
`
`2.0 and later
`
`Purpose
`Configures the maximum number of files and/or devices that can be open concurrently
`using file handles.
`Syntax
`
`FILES=n
`
`where:
`
`n
`
`is the maximum number of files and devices that can be open concurrently using file
`handles {8-255, default= 8).
`Description
`MS-DOS supports two methods of file access: file handles and file control blocks (FCBs).
`During i~itialization, MS-DOS allocates a data structure that holds information about files
`and/or devices opened with the handle, or extended-file-management, function calls. This
`structure resides inside the operating system's memory space and is accessed only by
`MS-DOS. (See USER COMMANDS: coNFIG.sYs: FCBs.) The default size of this data structure
`allows 8 files and/or devices to be open concurrently using the file-handle functions. The
`FILES command enables the user to change the size of the data structure. (Note that in(cid:173)
`creasing the size of the data structure decreases the amount of RAM available to applica(cid:173)
`tion programs.)
`
`the allocated data structure, whichever is less. Five of the 20 possible handles for a given 4
`
`The FILES command controls the maximum number of files and/or devices opened with ·
`handles for all active processes in the system combined. The limit on the number of files
`and/or devices opened for a single process using handles is 20 or the number of entries in
`
`process are automatically assigned to standard input, standard output, standard error, stan-
`dard auxiliary, and standard list. However, since standard input, standard output, and
`standard error all default to the same device (CON), only three of the allocated data-
`structure entries are actually expended. In addition, the preassigned standard device
`handles for a process can be closed and reused for other files and devices, if necessary.
`
`Section Ill: User Commands
`
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`ZTE (USA) 1007, Page 811
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`

`
`CONFIG.SYS: FILES
`
`Example
`To set the maximum number of files and/or devices that can be concurrently open using
`the handle functions to 20, insert the line
`
`FILES=20
`
`into the CONFIG.SYS file and restart the system.
`Message
`Unrecognized command in CONFIG.SYS
`An invalid number was specified in the FILES command.
`
`802
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`The MS-DOS Encyclopedia
`
`ZTE (USA) 1007, Page 812
`
`

`
`CONFIG.SYS: LASTDRIVE
`Set Highest Logical Drive
`
`CONFIG.SYS: LASTDRIVE
`
`3.0 and later
`
`Purpose
`Defines the highest letter that MS-DOS will recognize as a disk-drive code.
`Syntax
`
`LASTDRIVE=drive
`
`where:
`
`is a single letter (A-Z).
`
`drive
`Description
`MS-DOS block devices (floppy-disk drives, fixed-disk drives, and magnetic-tape drives)
`are referred to by logical drive codes consisting of a single letter from A through Z. In most
`MS-DOS systems, drives A and B are floppy-disk drives, drive C is a fixed disk, and drives
`D and above are such devices as additional fixed disks, RAMdisks, or network volumes. In
`some cases, a single physical drive (such as a very large fixed disk) is partitioned into two
`or more logical drives, each of which is assigned a drive letter.
`
`MS-DOS validates the drive code in a command or filename before carrying out a com(cid:173)
`mand. In the default case, MS-DOS recognizes a maximum of five drives (A-E), depend(cid:173)
`ing on the total number of default devices and devices incorporated into the system using
`installable device drivers. (MS-DOS does not consider a drive letter valid unles