DOS MS-DOS stands for Microsoft Disk Operating System. MS-DOS controls the computer’s hardware and provides an environment for programs to run. This system program must always be present when working with your computer.

DOS Components

IO.SYS A hidden file in the root directory of the primary drive. Provides the basic I/O capabilities for the system, allowing it the ability to communicate with the different peripherals. IO.SYS directs the overall process of loading the Operating System.

MSDOS.SYS Also a hidden file in the root directory sometimes called the kernal for DOS. When an application needs to access a device or peripheral, this file translates the request into actions that IO.SYS can perform.

CONFIG.SYS A user-configurable text file that usually contains device drivers and system setup values.

This is the Command Interpreter. COMMAND.COM This is the Command Interpreter. It can accept commands from the user, launch programs and pass this information to MSDOS.SYS.

Booting

Booting Booting is a process in which your computer gets initialized. This process includes initializing all your hardware components in your computer and get them to work together and to load your default operating system which will make your computer operational.

Two Types of Booting Cold Booting Hot Booting

Cold Booting When power to a computer is abruptly turned off, then turned back on. This starts the computer without first performing any shut-down procedure. Also known as hard reboot or cold reboot. It may be caused by power failure, be done by accident, or be done deliberately as a last resort to forcibly retrieve the system from instances of a system freeze, critical error or virus-inflicted DoS attack.

Hot Booting Restarting a computer under software control, without removing power or (directly) triggering a reset line. It usually, though not always, refers to an orderly shutdown and restarting of the machine. Also known as warm reboot.

Versions of DOS

VERSIONS OF DOS Version Date Comments 1.0 1981 Original version of MS-DOS. This was a renamed version of QDOS. 1.25 1982 This added support for double-sided disks. 2.0 1983 This added support for IBM's 10 MB hard disk, directories and double-density 5.25" floppy disks with capacities of 360 KB 2.11 Support for foreign and extended characters was added. 3.0 1984 Support for high-density (1.2 MB) floppy disks and 32 MB hard disks was added. 3.1 Network support was added.

VERSIONS OF DOS(Contd…) Date Comments 3.3 1987 This release was written to take advantage of IBM's PS/2 computer range. It added support for high density 3.5" floppy disks, more than one partition on hard disks (allowing use of disks bigger than 32 MB) and code pages. 4.0 1988 This version provided XMS support, support for partitions on hard disks up to 2 GB and a graphical shell. It also contained a large number of bugs and many programs refused to run on it. 4.01 1989 The bugs in version 4.0 were fixed.

VERSIONS OF DOS(Contd…) Date Comments 5.0 1991 This was a major upgrade. This version added support for IBM's new 2.88 MB floppy disks. An improved BASIC interpreter and text editor were included, as was a disk cache, an undelete utility and a hard-disk partition-table backup program. After the problems with MS-DOS 4, it also provided a utility to make programs think they were running on a different version of MS-DOS. 5.0a 1992/3 This was a minor bug fix which dealt with possibly catastrophic problems with UNDELETE and CHKDSK. 

VERSIONS OF DOS(Contd…) Date Comments 6.0 1993 It added a disk-compression utility called DoubleSpace, a basic anti-virus program and a disk defragmenter. It also finally included a MOVE command, an improved backup program, MSBACKUP and multiple boot configurations. Memory management was also improved by the addition of MEMMAKER. A number of older utilities, such as JOIN and RECOVER were removed. 6.2 Extra security was built into DoubleSpace following complaints of data loss. A new disk checker, SCANDISK, was also introduced, as well as improvements to DISKCOPY and SmartDrive.

VERSIONS OF DOS(Contd…) Date Comments 6.21 1993 Removed DoubleSpace. 6.22 1994 Microsoft licensed a disk-compression package called DoubleDisk from VertiSoft Systems and renamed it DriveSpace, which was included in this version. 7.0 1995 This version is part of the original version of Windows 95. It provides support for long filenames when Windows is running, but removes a large number of utilities. 7.1 1997 This version is part of OEM Service Release 2 and later of Windows 95. The main change is support for FAT 32 hard disks, a more efficient and robust way of storing data on large drives.

File Repository of data. Every file must have a name and certain rules must be followed when naming files: Each file must have a unique name. Filenames can contain from 1 to 8 characters with an optional extension consisting of a period (dot) followed by 1 to 3 characters. eg. february.txt A filename can consist of any alphabetical letters or numbers and can contain the characters _A$-!- {}()@. No other characters are acceptable. DOS has certain reserved words that cannot be used as file names.

Directory Can store any number of files. Each directory must have a unique name. Directory name can contain from 1 to 8 alphanumeric characters . A directory can be created by the user or by an application.

Three Categories of Directory Current Directory: In which user is working. Sub Directory: Directory within another directory. Root Directory: Starting point from which all other directories branch out. It is represented by \ . C : \ TC \ TEST > Drive Root Directory Sub directory of TC

Accessing the command prompt through the Windows Start menu

Initial DOS Prompt

Output Redirection The output of DOS command can be directed to another device or to a disk file by using redirection output symbol(>). C:\> dir > dirlist

Input Redirection Command input can be accepted from any device that is capable of supplying data to DOS by using input redirection symbol(<). C:\> more<abc.txt C:\>label<name.txt

Piping The "pipe" redirects the output of a program or command to a another command. It can be used as command1 | command2 C:\>dir | more C:\>dir d: | sort | more

Wildcard Characters Serve as replacement entries for a single or a set of characters. Two wildcard characters are: ? Stands for single character replacement * stands for replacement of any number of characters

Examples: Wildcard Characters Typical interpretation *.* All files with all extensions. *letter*.* All files with "letter" anywhere in its name. *smith.* All files with names ending with "smith" (or "Smith") Test?.txt All files named "test" + one character and with txt extensions (eg test1.txt, but not test-a.txt nor test.txt) ?e*.* All files with an "e" as second letter in their names

DOS Commands An instruction written in computer acceptable language that user types to execute a specific operation on the DOS prompt. The command interpreter accepts input in a specific form known as syntax.

General Format of DOS Command

Two Types of Commands Internal commands External commands

INTERNAL DOS COMMANDS Internal Commands are located in memory and do not require and further disk access when they are used. COPY, DEL, DIR, VER, TYPE, PRINT

EXTERNAL DOS COMMANDS They reside on the DOS disk and require a disk access to be used CHKDSK, FORMAT, DISKCOPY ,MD,CD,RD