Tech Master Guide

Disk Operating System (DOS) 6.22

The OS is a collection of programs that manages and controls the entire operations of the computer. It controls all the I/O devices, processor, memory etc and runs software. The OS supervises the interaction between system and user.

Booting: - Loading the OS into the main memory of the computer is known as booting. The DOS can be loaded into memory in two ways, clod and warm booting. Booting a computer while in “OFF” position is known as cold booting. Rebooting a system while OS is already in the main memory, using reset button or pressing Ctrl + Alt + Delete is known as warm booting.

DOS Prompt: - The OS may be loaded into the main memory either from floppy or hard disk, after booting the DOS the system displays the DOS prompt like a:\> when the DOS is loaded from floppy (If DOS is loaded from hard disk the DOS prompt like c:\>). All the commands are entered at this prompt.

File name: - The data must be stored under a name for the better retrieval and processing performance. In DOS, the file name has two parts, primary and extension part. The primary part is must and can be up to eight characters length. The extension part is optional and can be up to three characters length. Even though all the alpha numeric characters are allowed for naming a file, certain reserved names are given bellow, which cannot be used as file name. E.g.: Aux, Com1, Com2, Cpt1, prn etc…

System files of DOS: - The MS-DOS consists of two hidden files io.sys and msdos.sys and command interpreter named command.com. The file io.sys and msdos.sys manages the processor, memory, I/O devices and file system. The command.com interprets and process all commands that are entered.

In MS-DOS there are two types of commands, internal and external.
The internal commands are an integral part of command interpreter E.g.: dir, cls, date etc. External commands are not a part of command interpreter, so the corresponding file should be loaded into the memory to execute. These are files with extension Exe, Com and Bat E.g.: Tree, Format, fdisk etc.

DOS Commands

Internal Commands

Date To display the current date or change the date.
Time To display the current time or change the time.
Dir To display the list of files & directories in the current position. It displays the name, size, date & time of modification etc…

The command line switches are:

/p Show page wise
/w Show width wise
/s Show all files in all sub-directories also
/on Sort the order of name
/oe Sort the order of extinction
/od Sort the order of date
cls To clear the screen.
Ver To display the version of currently active DOS
Vol To display the Volume label & serial number of the disk.
Copy con To create a new file.
E.g.: - copy con abcdef.asd
Ctrl+Z / F6 (To save the file).
Type To display the contents of a file.
Copy To create a duplicate copy of a file.
Ren To change the name of a file.
Del To delete (Remove) a file from the disk.

Wild card characters

Wild card characters are used to select a group of files. There are two special characters that can be used as wild card characters, “* and ?”.
‘?’ is used to replace a single character position. ‘*’ is used to replace 1 to 8 characters in the primary part and 1 to 3 characters in the extinction part.
E.g.: -
Dir *.com To list the file names with extension '.com'
Dir a*.* To list the file names starting with 'a'
Dir *. To list the file names having no extensions
Dir ?a*.* To list the file names having second character of primary part is 'a'.

Sub directory

Mkdir/md Make directory
Chdir/cd To transfer the control in an existing sub-directory
Cd\ To return the root directory
Cd.. To return the previous sub-directory
Rmdir/rd To remove a directory

EXTERNAL COMMANDS

Label To create/change/delete the label of a disk
Mem To display the report about memory
Chkdsk To analyze the disk
Tree To display the sub-directory structure graphically
Deltree To delete the tree
Disk copy To copy the contents of a floppy to another
Disk comp To compare the contents of two floppy disks
Scandisk To scan and repair the hard disk

FORMATTING

Format This command divided the storage media into tracks and sectors. It also create Fat and Dir table.
/U Unconditional formatting
/Q Quick formatting
/S To copy the system files to the target disk
Sys To copy the system files to the disk
Xcopy To copy Files and sub-directories in to another location
/p To copy the files selectively
/s To copy the files and sub-directories of a specified directory.
/e To copy empty directory also

Attrib

+r To set read only
-r To remove read only
+h To set hidden
-h To remove hidden
+s To set system
-s To remove system
+a To set archive
-a To remove archive
Dir/ar To display read only
Dir/ah To display hidden only
Dir/as To display system files
Dir/aa To display archive only
Edit To get text editor
Defrag To arrange data