CONFIG.txt

               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).