BIOS, CRDOS. Part 4.

System configuration.
DOS loading occurs according to the following scenario. The loader
, hardwired into ROM, reads the DOS loader
from the boot disk and transfers control to it. The DOS loader, in turn
reads two system files IO.SYS and CRDOS.SYS into memory and
transfers control to the latter file.
After initialization, on the disk specified as the system
(it is not necessarily loaded from it), the file
CONFIG.SYS is searched and the system is configured in accordance with it. If there is no CONFIG.SYS file, configuration
occurs by default.

Commands accepted from the configuration file:
BREAK= { ON | OFF } - setting (default-
)/removing the mode of interrupting the work of programs by pressing
^C.
HELP= { FULL | BRIEF | OFF } -installation/disabling of the hint (FULL by default).
SHELL=file_name [, address] -installation of another command processor.
DEVICE=file_name [parameters] -loading the driver.

After configuration is completedthe command processor is searched and loaded. When using standard
CCP, the line 'SHELL=...' (from the CONFIG.SYS file) can be omitted.
Typically, the command processor is loaded at the end of the OTP and when it is overwritten by application programs, it is loaded from disk.
In the standard shell file, a significant
space is occupied by help, i.e. detailed description of CCP commands. In
the 'HELP=...' line you can set whether to support a full hint, an abbreviated one (a list of commands with short usage),
or no hint at all. In the last two options
loading CCP will be faster, and CCP will
take up less memory.
After loading the command processor, the batch file AUTOEXEC.BAT is searched
and executed.

NOTE. For CR-DOS version 1.5, it was not planned to support extended batch work and batch files with commands for, if, echo, etc., as well as reassignment of input and output using the commands '<', '>' and '|'.

DOS transit utilities.
The size of the command processor is limited to reasonable limits and it is impossible to accommodate all utilities. In this connection,
they are recorded in separate files. BrieflyWe will describe the main
of them.

ATTRIB.COM - utility for setting attributes on files and disks.
VDISK.SYS is a driver for virtual disks located in
extended or main memory.
DD.COM -disk doctor. Finding and correcting failures
of the file structure on disks, localization
of bad memory cells on disks.
SD.COM - disk sorting. Sorting files on disk
according to a given scheme. To speed up loading of files, it makes sense to place the required file
closer to the beginning of the disk.
MAKESYS.COM - makes the disk a system one. The disk may not be empty. For ROM disks, it produces a printout of codes
or writes a file with codes
to another disk for the ROM programmer.
ASSIGN.COM - changes drive designations (for example, replacing A:
with C:), and also performs "gluing" several
disks into one.
IOFLOPPY.COM - file exchange between RAM disks and floppy disk-
mi.

+-+--+--+--+--+--+--+- ROM - CHANGER -+--+--+--+--+--+---+
+-+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+---+

ROM - K556RT5 512 bytes

***** Bootloader program, algorithm *****

* Begin *
* Init
* Led On
Yes+-+- ? PPA-3 installed? -+-+No
+--> * Load Segment +-+-> * Led Off
Yes+-+- ? Media = E5? -+--+--+--+-> * Halt
+--> * Load Data No
* Led Blinking
* End *

0 1 2 3 4 5 6 7
+-+--+--+--+--+--+--+--+--+-+
SEGMENT: │MD│x│BegROM│LastROM│BegLoad│
+-+--+--+--+--+--+--+--+--+-+
MD - media descriptor: E5
x - not used
BegROM - beginning of the program in ROM
LastROM - end of the program in ROM
BegLoad - start loading the program into RAM

-+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+---

What about crushing the baby?