MS-DOS/v2.0/source/CONFIG.txt

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Configuration files in MSDOS 2.0
In many cases, there are installation-specific configurations
of the DOS that are need to be set up at boot time. It is
considered ugly for a user/OEM to have to re-build the DOS to
include special drivers or to include a particular number of
device drivers. The configuration file allows a user/OEM to
configure his system without extra work.
The configuration file is simply an ASCII file that has
certain commands for the boot task. The boot process is as
follows:
Disk boot sector is read. This contains enough code to
read the DOS and the initial BIOS.
This DOS and initial BIOS are read.
A long jump to the BIOSINIT routine is made. A variety of
BIOS initializations are done.
A long jump to the SYSINIT routine in the SYSINIT module
is made. This module (supplied by MICROSOFT) will
initialize the DOS and read the configuration file
CONFIG.SYS, if it exists, to perform device instalation
and various other user settable things. Its final task is
to EXEC the command interpreter, which finishes the
bootstrap process.
The following are a list of commands for the configuration
file CONFIG.SYS:
BUFFERS = <number>
This is the number of additional sector buffers to add
to the system list. The effect of several BUFFERS
commands is to allocate a series of buffers.
FILES = <number>
This is the number of open files that the XENIX system
calls can access.
DEVICE = <filename>
This installs the device driver in <filename> into the
system list.
BREAK = <ON or OFF>
If ON is specified (the default is OFF), a check for
^C at the console input will be made every time the
system is called. ON improves the ability to abort
programs over previous versions of the DOS.
SWITCHAR = <char>
Causes the DOS to return <char> as the current switch
designator character when the DOS call to return the
switch character is made. Default is '/'.
AVAILDEV = <TRUE or FALSE>
The default is TRUE which means both /dev/<dev> and
<dev> will reference the device <dev>. If FALSE is
selected, only /dev/<dev> refers to device <dev>,
<dev> by itself means a file in the current directory
with the same name as one of the devices.
SHELL = <filename>
This begins execution of the shell (top-level command
processor) from <filename>.
A typical configuration file might look like this:
BUFFERS = 10
FILES = 10
DEVICE = /bin/network.sys
BREAK = ON
SWITCHAR = -
SHELL = a:/bin/command.com a:/bin -p
The default value for BUFFERS is OEM specific in that the
OEM can specify the number in the BIOS. A typical value is 2,
the minimal value is one. The default value for FILES is
usually 8 (as above it may be set by OEM BIOS) , so "FILES =
10" actually allocates only 2 new file channels. If a number
less than or equal to five is specified, the command is
ignored. BREAK defaults to OFF, SWITCHAR to /, and AVAILDEV
to TRUE. NOTE that the setting of SWITCHAR may effect
characters used on the SHELL line (this is true of
COMMAND.COM).