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2. Introduction to DOS Operating System

1. The DOS, OS - 2. History - 3. Keys and special characters - 4. Devices - 5. When the computer starts.

This online training is based on DOS 5.0, 6.0 and 6.2 and takes orders for current Windows systems. Some commands do not work anymore or you changed options with the current Windows (2003 or XP). Currently, DOS is almost used that order networks, or the recovery console, it is mainly for this purpose that we will see these commands.

1. The DOS as Operating system

DOS is designed for the early IBM XT (compatible X 86 processors). Unlike the time operating systems, it is not integrated in ROM memory, but a floppy disk or installed on the hard disk. It works in text mode using a prompt: orders must be known by the user (they are not very complex and included related English words). The graphical interface using the mouse came later with an additional layer (Windows 2.0, 3.0, 3.1, 3.11 - Workgroups).

DOS is initially designed to manage hard disks and floppy disks, as well as their use for backup and recovery of files (data, programs,...), including their organization in directories. Different commands also allow to prepare media as the FDISK ou FORMAT commands. By managing directly coupled to the setup BIOS, this operating system will serve as an interface between the user and PC electronics

The DOS commands are separated into two types:

  1. internal commands: directly executable, are part of the core of the operating system.
  2. external commands: separated from the original program, are additional programs. To run an external command, will also report its location on the hard disk or floppy disk (possibly via the PATH command).

2. History

DOS (Disk Operating System) is the first operating system used with the PC. It was developed by Microsoft for the firm IBM and computer of type XT. It was developed in parallel under 3 names following the seller: PC - DOS for IBM, for Novell DR - DOS and MS-DOS in all other firms (marketed by Microsoft). They are equivalent, only a few small differences in commands options are present.

Like all operating systems, DOS is developed to serve as an interface between the electronics on the one hand and the user on the other hand. It includes no GUI, it is a text-based operating system. Microsoft has circumvented the problem by developing the Windows 2.0, 3.0, 3.1, 3.11, a sort of graphic add-on.

Even if the current Windows versions still include a DOS interface, it is no longer the major operating system. These limited DOS functionality are predominantly used in command networks.

3. The keys and specific characters of DOS.

Some special commands are used by DOS. Later in this course, <key>will mean press the keyboard <key>, <Key1>+ <key2> means press key 2 leaving the key 1.


<ALT>+ 94 gives the character ' ^', this combination is based on the ascii code.

<ALT>+ <CTRL>+ <SUPP>: restarts the computer

<CTRL>+ <C>: stops the execution of a command

<CTRL>+ <S>: temporarily stops a DOS instruction, it resumed by pressing any key, used for example with the DIR command

<ALT>+ <CTRL>+<f1> puts the Qwerty keyboard if the keyboard has been defined as azerty (Belgian, French,...)

<ALT>+ <CTRL>+<f2> resets the AZERTY keyboard

For the majority of the commands, the command name followed by /? Displays help.

4. The devices

Some commands recognize the name of the communication ports on the what devices can be connected:

COM: console screen and the keyboard

LPT1: output parallel number 1 (address $378)

PRN: equal to lpt1

COM1: serial port number 1 (address $3F8)

COM2: serial port number 2 (address $3E8)

These names are only used in specific commands. DOS do not recognize USB ports.

Note, all the commands to create a text file in the link of a screen display. Simply add > filename. Example DIR >content.txt will create the content.txt file that contains the list of folders and files in the current directory.

5. Start the computer

When you start the computer, the processor bed first the instructions included in the BIOS. Then, it reads the instructions on the disk (if a diskette is inserted) or on the hard disk. It will first read 3 hidden system files:, io.sys, and ms.sys (in the case of a Microsoft DOS).

Then there are 2 optional commands files:

We will see these 2 files in detail in a later chapter.

Follow chapter for OS training > Files and directories command in DOS

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