Types of DOS Commands

There are two types of DOS Commands:

1. Internal Commands

2. External Commands


Internal Commands

Internal commands are a part of the DOS program COMMAND.COM and are loaded into memory when you boot your computer. These commands are needed to be used most often, although they are not seen when we display the disk directory of filenames on our screen. Some internal DOS commands are:


CLS

This command is used to clear the screen of a monitor.

Syntax: CLS


DIR

This command is used to display a list of current directly files and subdirectories.

Syntax: DIR[drive:][path][filename][/p][1w]


CHDIR (CD)

This command is used to display the current directory or changes in the current (default) directory.

Syntax: CD[drive:][path]


DEL

This command is used to deletes one or more specified files from the disk.

Syntax: DEL[drive][path]file name[/p]

e.g. DEL Aslam.Doc


External Commands

External Commands are programs, which exist on the DOS disk or the hard disk. They are run when you type their name on the command line. For example, typing FORMAT at the DOS prompt results in a program called FORMAT.COM being executed.

External Commands are not frequently used and DOS saves valuable memory space by loading them only when required. Some the external commands are:


CHKDSK

This command is used to checks the validity of a disk and reports the total space, used and free space on the selected disk.

Syntax: CHKDSK [drive][path][/f][/v]


SYS

This command is used to create a bootable drive and installs the main DOS files.

Syntax: SYS[drive:][path]drive2:

e.g. SYS A:


TREE

This command is used to display directory structure.

Syntax: TREE[drive:][path][/f][/a]


XCOPY

This commands is used to copy files (except hidden and system files) and directories, including sub directories.

Syntax: XCOPY source [destination][/a|/m][/d:date][/p][/s][/e][/v][/w]

e.g. XCOPY *.*A:


DELTREE

This command is used to delete all files and sub directories in a directory.

Syntax: DELTREE[/Y][pathname]

Booting the System

The term boot or bootstrap, when used with computers, means start or startup. When we boot our computers, we are turning it on and loading the Disk Operating System (DOS) into our computer's memory. The sequence of events that occur between the time you turn on your computer and the time it is ready for you to issue commands is referred to as the boot process. At the completion of the boot up process the system gives a DOS Prompt as soon as it is ready for operations