(Disk Operating System)

History of DOS
Missed Meeting, missed opportunities, When Gary Kildall President of CPM OS missed his meeting with IBM representatives, this opened the door to a small software developer company called Microsoft. Led by its Co founders Bill Gates and Paul Allen they were able to purchase the rights to QDOS and later renamed it to MS DOS. Microsoft were able to license the OS to IBM and other computer manufacturers. The rest as they say were History.

Fundamental concepts of MS DOS

DOS version 1.0 (1981)
DOS version 6.22 (1994)

System Prompt
A set of characters followed by a blinking cursor. This is commonly called as the command prompt interface. Example: C:\>

Default Disk Drives
The A and B drive is reserved for floppy drives
The C drive is where the OS usually boots up and can go up to letter Z

DOS Boot up Sequence

IO.SYS – A binary file that provides basic input/output interface between the ROM BIOS and the Hardware
MSDOS.SYS – A binary file considered to be the core of the DOS operating system
CONFIG.SYS – A text file used to load drivers and memory managers and also use to configure the system to the user’s needs
COMMAND.COM – DOS user interface loads the command prompt which interprets DOS commands
AUTOEXEC.BAT – A text file that contains setting up display settings, environment variables and routines

DOS Memory Management

MS DOS configuration files and settings software

CONFIG.SYS - loads device drivers and memory managers

To view CONFIG.SYS
C:>TYPE CONFIG.SYS

To edit or change setting in CONFIG.SYS
C:>EDIT CONFIG.SYS

Typical CONFIG.SYS Screen

DEVICE=C:\DOS\HIMEM.SYS (must be the first line)
DEVICE=C:\DOS\EMM386.EXE
DOS=HIGH, UMB
BUFFERS = 15
FILES = 30
DEVICEHIGH=C:\DOS\SETVER.EXE
DEVICEHIGH=C:\DOS\SMARTDRV.EXE
DEVICEHIGH=C:\SOUND\DRV\SYS/BLASTER = A: 220 1:5 (example of sound card driver)

CONFIG.SYS Commands

DEVICE - loads drivers from conventional memory
DEVICEHIGH - loads drivers from upper memory area
DOS=HIGH, UMB - loads DOS into high memory in a upper memory block
BUFFERS - is an area in memory where data waiting to be read or written is temporarily stored
FILES - sets how many files can be open at one time, 30 is default

CONFIG.SYS Drivers

EMM386.EXE - memory manager use to open up the expanded memory area
HIMEM.SYS - memory manager use to open up the extended memory area
SETVER.EXE - loads the correct DOS version table for different versions of DOS
SMARTDRIVE - creates disk caching in extended or expanded memory

AUTOEXEC.BAT - is where the user creates and fine tunes the function and appearance of MS DOS environment

Typical AUTOEXEC.BAT Screen

@echo off
PROMPT=$P$G
PATH = C:\DOS
SET TEMP=C:\TEMP
SET BLASTER=A220 15 D1 H5 P330 E620 T6
LH C:\MOUSE\MOUSE.EXE

AUTOEXEC.BAT commands

@echo off- tells DOS to just read lines but not echo back to the screen
PROMPT - set the prompt statement for DOS
PATH - sets the path statements so executable files can load in DOS
SET - defines environment variables and settings
LH - load high command

F5 - Bypasses the CONFIG.SYS and AUTOEXE.BAT during boot up

F8 - Step by step confirmation of each line in CONFIG.SYS and AUTOEXEC.BAT

Memory Management

MEM - displays a quick status report of available memory and memory usage in your computer,especially useful in determining your conventional and upper memory usage

MSD - A DOS diagnostics program (DOS 6.22)

MEMMAKER - A DOS utility program use to optimize memory (DOS 6.22)

DOS Optimization programs

SCANDISK - A disk utility tool use to correct disk problems it will mark bad sectors, directory structures, lost clusters and cross linked files

DEFRAG - Speeds up disk access by rearranging files into contiguous clusters

MSAV - Anti virus program available in DOS