# What is disk operating system (DOS).

disk operating system (DOS).

DOS stands for disk operating system. It is a character based or command based operating system. It was the first operating system for desktop computers. Initially it was developed for IBM. Later MS-DOS was developed. Today Microsoft operating systems supports Dos. It is 16 bit operating system. It does not support multi users. It is a character based operating system means as a user to operate with computer using dos he has to work with all commands. It does not support GUI (Graphical user Interface).Many dos based games are developed.

Dos as many versions like dos 1.0, 2.0, 5.0, 5.5

Dos 6.2, 6.22, 7.0 .Dos 7.0 is available in window95 and later operating systems. Basically dos have two types of commands.

1. Internal Commands
2. External Commands.

It is a small program that was resided in ROM(read only memory).Whenever is system is on then automatically that the program which was written in  ROM will execute itself and loads operating system from the disk. It is a part of BIOS.

Internal Commands

Internal Commands are those commands all the commands are loaded into ram when the system is on. These commands are not resided on disk. These Internal Commands are written in COMMAND.COM. Different Internal Commands are

DATE

TIME

PATH

VER

VOL

PROMPT

REM

MD

TYPE

SET

DEL

COPY

CLS

ECHO

EXIT

External Commands

External Commands are those commands all the commands are resided on disk. These commands are .com, .exe, .bat  both internal  and external commands run from ms-dos prompt. Different types of external commands are

ATTRIB

CHKDSK

APPEND

BACKUP

DISKCOPY

DISKCOMP

EDIT

FDISK

FORMAT

LABEL

MORE

SYS

TREE

XCOPY

UNDELETE