What is MS-DOS (Microsoft Disk Operating System)?

MS-DOS was a PC operating system created by Microsoft from QDOS and initially used by computers manufactured by IBM.

What is MS-DOS in a Computer?

It is the abbreviation of Microsoft Disk Operating System, an operating system created by Microsoft and installed on most PCs. DOS is, in addition to an operating system, a set of programs that allow us to manipulate the information found on disks. In this way, we can work with them efficiently, comfortably, and quickly. In addition, DOS coordinates the work of the microprocessor. So that everything works well inside our computers.

Microsoft has been developing DOS since its first version in 1981. Existing versions are used to fix bugs detected in the previous version or to improve specific parts of the program. If the variation is seen in the first figure, it is essentially to take advantage of its advantages. This means that significant changes have been made, for example, regarding the benefits of new microprocessors.

MS-DOS History

Although it is perhaps an old and forgotten operating system by most users, it forms the basis of the most current operating system.

It began with the purchase of an operating system called QDOS by Microsoft in 1981, which, after making a few changes, became the first version of the Microsoft MS-DOS 1.0 operating system.

A series of changes occur in the operating system until it reaches version 7.1, where MS-DOS ceases to exist as such and becomes an integrated part of the Windows operating system.

MS-DOS Versions

Among the versions or developments of the DOS operating system:

1) PC DOS 1.0

PC DOS 1.0 is the first version of DOS released in 1981 in addition to IBM-PC. It supports 16 Kb RAM and 5.25 inch single-sided 160 Kb floppy disks. It allows files with .com and .exe extensions. It contains the COMMAND.COM command interpreter.

2) PC DOS 1x

Many bugs were fixed in the PC DOS 1.1 version, which supports dual-density floppy disks. In 1982, version 1.25 was released, adding support for double-sided floppy disks.

With version 2.0 added support for IBM 10 MB hard drives and the possibility to read 5.25 floppy disks with 360Kb capacity, it wasn’t until 1983, the following year, that the system had more functionality.

In the same year, new keyboard characters were added to version 2.11.

In 1984, Microsoft added support for 1.2 MB high-density disks in MS-DOS 3.0 and the possibility of installing a hard disk with a maximum of 32 MB. In the same year, support for MS networks was added in version 3.1.

Three years later, in 1987, with the release of version 3.3 and the use of hard drives larger than 32 MB, it was allowed to support existing 3.3 and known 3.5″ floppy disks.

Microsoft released version 4.0, and with it, XMS memory support and the possibility to include hard drives up to 2GB. It should be noted that this version is the biggest disaster carried out by the company, as it is full of failures. This was fixed in version 4.01, which corrected all these issues and errors in 1989.

One of the most relevant advances in MS-DOS history is the transition from version 4.01 to version 5.0 in 1991, where DOS could load programs into the high-memory part of the system using higher memory. In version 5.0, the BASIC programmer and famous EDIT editor have been added.

A utility has also been added to run UNDELETE (Recovery of deleted files), FDISK (Partition Management) utilities, and SETVER programs designed for previous versions of MS-DOS. Some problems with UNDELETE and CHKDSK in version 5.0a were resolved at the end of 1992.

3) MS-DOS 6.0

It appears with many new features that are responsible for compressing the disk and thus have more usable space, including a basic antivirus (MSAV), a defragmenter (DEFRAG), a memory manager (MEMMAKER), and some older features.

In the same year, version 6.2 was released in 1992, which added security to the data loss of Doublespace and resolved issues with a new disk scanner, SCANDISK, DISKCOPY, and SmartDrive.

4) MS-DOS 6.21

Appearing in 1993 in the same year, Microsoft was suppressing Doublespace and was looking for a new alternative for this utility.

A year later, the solution to the Doublespace problem in 1994, Stac Electronics, which chose to be included in version 6.22, appears to be the benefit of the Drivespace company.

5) PC DOS 6.3

PC DOS 6.3 was released in April 1994. Already with the release of Microsoft Windows 95 in 1995, MS-DOS was taken to a secondary level.

However, the MS-DOS system is still a new version 7.0 in 1995, where many utilities have been fixed and provide support for long names. Utilities deleted from the previous operating system can be found in the Windows 95 CD\other\oldmsdos directory.

6) MS-DOS 7.1

In 1997, Windows 95 OSR2 appeared, and with it, a comprehensive revision of the DOS system added support for FAT32 partitions, and this is the history of MS-DOS versions. It was later integrated into Windows 98 and 98 SE. Supports FAT32 file systems.

7) MS-DOS 8.0

It is included in Windows Me. It is the latest version of MS-DOS.

8) PC DOS 2000

It is the new version that solves the problem of the year 2000.

Currently, the MS-DOS operating system is very little used. In most cases, it is used only when Windows cannot perform its task or Windows fails. Many technicians in the computing area use MS-DOS to perform PC maintenance, setup, formatting, and partitioning of hard drives and scans.

Characteristics

MS-DOS is a single-user, single-task operating system for personal computers.

MS-DOS Commands

Here are some of the commands that MS-DOS uses and that are currently available from the command line on Windows operating systems:

External Commands

ATTRIB: Displays the attributes of directories and files without parameters. It replaces the attributes of directories and files with parameters.

The attributes of directories and files are read (r), write (w), file (a), hidden (h), and system (s).

Parameters: Attrib (plus or minus) and the letters r, w, a, and h “v.” Example: Attrib + r *. * (Read-only attribute for all files in this directory)

These parameters can be used together:

Redirections

<: Redirection of the standard entry.

>: Redirection of the standard entry. If there is no file, it creates it and overwrites its content, if any.

>>: Redirects standard output to an existing file. If there is no file, it creates, if any, adds the result of the command after the previous content of the file.

Control Mechanisms

MS-DOS is a single-user, single-task operating system. By meeting these two conditions, the processor is always specific to executing a process, so the planning of the processor is simple and dedicated to the only efficient method that can exist at any time.

MS-DOS includes five essential elements for controlling and deploying processes:

1. ROM-BIOS.: It is an input and output management program between the operating system and the computer’s primary devices.
2. IO.SYS.: A series of instructions for transferring input/output from peripherals to memory. It initializes the system and includes built-in device drivers.
3. MSDOS.SYS.: It is the MS-DOS kernel with instructions for checking diskettes. It is a program that manages files, directories, memory, and media.
4. DBLSPACE.BIN.: It is the kernel controller of the hard disk compressor to increase the storage capacity of the disk, available from version 6 of MS-DOS. This drive performs all file compression and decompression operations and can be moved to higher memory than traditional memory.
5. COMMAND.COM.: It is the interpreter of commands that the user communicates with the computer. It interprets the written commands and includes internal DOS commands that are not displayed in the system directory.

The IO.SYS, MSDOS.SYS and DBLSPACE.BIN files are hidden, meaning they do not appear when listing the directory and are loaded from disk to computer memory when starting the directory. In DOS control, there are two ways to boot the system:

1. It caches input and output devices, keyboards, monitors, hard drives, floppy disks, and memory (RAM). Then, it looks at the floppy drive first, and if there is a floppy disk with the operating system, it starts it. Otherwise, it looks at the hard drive.
2. It is performed by turning off the computer with the reset button or Ctrl+Alt+Del. All previous tests have not been done and are installed directly. It is usually used after the operating system crashes or a computer crashes.

Among the programs that interfere with the control of the DOS operating system:

Bootstrap

It is responsible for starting the computer. They are also known as IPL (initial program load). Bootstrap program is programmed in the Basic program. The first program in the ROM reads the disk startup program, which determines whether the IBMBIOS.COM and IBMDOS.COM files are on the disk.

If it finds the files, it first runs IBMBIOS.COM, which consists of two parts:

BIOS: It is the department responsible for the control of environmental units.
SYSINIT: It is responsible for determining the amount of continuous memory in the computer.

It then runs IBMDOS.COM, and SYSINIT goes from the low part of the computer memory to the high part and leaves the low part to IBMDOS. The first thing it does is control the peripherals to ensure that they work correctly. After controlling peripherals, SYSINIT returns and calls Kernel services to execute the CONFIG.SYS file.

Finally, SYSINIT calls DOS services and installs COMMAND.COM. The launch party will load the AUTOEXEC.BAT file.

After that, the startup partition SYSINIT and COMMAND.COM are cleared from memory.

BIOS

Refers to the Basic Input/Output System. It is specific to each manufacturer and is responsible for controlling the input and output hardware units. The BIOS is loaded by reading the IBMBIOS.COM or IO.SYS file and saved in RAM.

IBMDOS.COM

It is the core or core of the system. Its functions are file management, memory management, and the creation of other programs. It is independent of the hardware used. It includes a number of services.

COMMAND.COM

It is an interface between the user and the device through a series of prompts and response messages for user commands. He is responsible for grammatical analysis and manages the user’s commands.

COMMAND.COM is also responsible for managing interruptions. The cutting system has a simple priorities hierarchy to deal with interruptions caused by peripherals. When an interruption treatment ends, the control is returned to the running program when the interruption occurs.

It is also about addressing any error that may occur during the execution of a program, returning control to the program where the error occurred, and, if possible, MSDOS.

It manages the internal commands directly linked to it. It is not mandatory to use it.

It is divided into three parts:

1. Settled: It is installed under the memory, on top of the kernel and BIOS. Ctrl + Break processes critical errors using Ctrl + C keys.
2. Initialization partition: It is loaded on top of the built-in partition and is responsible for processing the AUTOEXEC.BAT file, then it is deleted from the RAM.
3. Temporary module: It is loaded into the upper part of the memory, and its purpose is to prepare the command prompt or command prompt required to enter and execute instructions. It is installed when needed and removed after the command is executed.

CONFIG.SYS

Config.sys is a system file created or modified with any text editor.

It runs before Autoexec.bat and includes a set of computer configuration commands. Some of its parameters show the number of files that can be opened simultaneously. It has no size limitation and should be located at the root of the disk. In addition to the files, there are other “typical” commands in this file:

• Buffers: It is the intermediate storage area where things are temporarily stored to transfer data.
• Country: Indicates the country you are working in so that the correct country characters are displayed.
• Device: Used to install mouse, keyboard, and other features.
• Break: It tells DOS whether to check by pressing Ctrl + C or Ctrl + Break.
• Lastdrive: Specifies the last letter of the disk drive that the system will recognize.

AUTOEXEC.BAT

This is a batch file. It is used to start a series of non-essential functions, enter data, activate system controls, and automatically load programs.

If there is an operating system, it runs automatically. It has no size limitation and should be in the directory where the system is booting. There are usually a few commands included:

• Keybsp: Updates the keyboard.
• Path: Searches for a program in any folder specified in this command.
• Set: It contains environment variables and their corresponding values.

Like any batch file, AUTOEXEC.BAT has the same features as others: it has a BAT extension, contains commands, can be run by entering its name after the command prompt, and if we press Ctrl + Pause, the process is interrupted. In addition, three unique features have been added:

• It has a mandatory name and extension: it should always be called AUTOEXEC.BAT.
• The computer runs every time it starts up. Otherwise, It runs three commands instead: Date, Time, and Ver.
• It should be located in the root directory of the boot drive.

The AUTOEXEC.BAT file also contains commands to configure the user’s language.

Therefore, the following three basic modules should be included in the AUTOEXEC.BAT file:

• Configuring environment variables.
• Instructions to choose the language.
• Orders for installing built-in programs.

The first set of commands contains the definition of environment variables. Note that PATH and PROMPT variables can be defined by the Set command or by specially designed commands called Path and Prompt.