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

MS-DOS is an acronym that stands for Microsoft Disk Operating System and is a version of the first widely installed operating system for personal computers. 

Developed by Microsoft, it is essentially the same as the OS created by Bill Gates’s company for IBM called Personal Computer – Disk Operating System (PC-DOS). It is considered a pioneering operating system that paved the way for modern computer systems.

IBM licensed and marketed MS-DOS in 1981 under the name PC-DOS for use on their personal computers. MS-DOS was originally designed for use on x86 architecture computers and went through eight major versions throughout its lifespan. 

Despite its success, MS-DOS was officially retired from all active support in 2006, marking the end of an era for one of the most influential operating systems in computer history.

While both DOS systems, PC-DOS and MS-DOS, were commonly referred to simply as “Disk Operating System” by users, the latter was a non-graphical, command-driven operating system with a line-oriented interface. 

The user interface was relatively simple but not particularly user-friendly. To enter an MS-DOS command, users were presented with a prompt that looked like this:

C:>

The default command prompt in MS-DOS displays the disk drive that is currently in use. This type of user interface, where the user inputs commands in response to a text prompt, is known as a command-line interface (CLI). 

In a CLI, the user types commands using a keyboard and receive text-based feedback in response.

In the above example, the drive letter “C:” represents the primary hard disk drive of the system running MS-DOS. 

However, if MS-DOS were booted from a floppy disk, the command prompt would display as A:>, where “A:” represents the primary floppy disk drive. This meant that all MS-DOS commands entered by the user would be executed from the floppy disk drive instead of the hard disk drive.

The initial version of Microsoft Windows was essentially an application that ran on top of MS-DOS. Over time, Windows evolved into a standalone operating system, but it continued to include support for MS-DOS. 

Nowadays, Windows operating systems use emulation to provide support for DOS or a DOS-like user interface for specific purposes. This support is typically used for running legacy software or performing low-level system maintenance tasks that require a command-line interface.

Before the advent of the personal computer in the 1970s, IBM had a different and unrelated operating system called DOS (Disk Operating System), which ran on smaller business computers such as the IBM 370. This early DOS was designed to manage disk storage and perform basic file management functions. 

However, as larger and more sophisticated operating systems became available, IBM eventually replaced DOS with VSE (Virtual Storage Extended) OS. VSE was a more advanced operating system that provided a higher degree of compatibility and functionality for IBM’s business customers.

Why is MS-DOS used?

While most computer users today prefer modern operating systems with a graphical user interface (GUI), there are still certain situations where MS-DOS may be preferable. Some of the reasons to use MS-DOS include:

• Education and Research: MS-DOS can be used as a learning tool for understanding the basics of operating system functionality. The availability of the source code for two versions of MS-DOS from Microsoft, as well as emulators and OSes providing MS-DOS functionality, also makes it a useful platform for research.

• Legacy Systems: Many organizations continue to rely on MS-DOS due to budget constraints or the preference for legacy systems that have worked reliably for decades.

• Embedded Systems: MS-DOS is an important operating system for embedded systems that use the x86 processor architecture. It is also used on legacy embedded devices that may have been in use for years. These embedded systems can sometimes be updated to run up-to-date versions of compatible OSes.

• Classic Games: MS-DOS is popular for classic computer games that were developed and supported only on this operating system.

• User Inertia: Some people and organizations may continue to use MS-DOS due to inertia or a preference to skip updates. This is especially true for individuals who are comfortable with older software and do not wish to learn new programs.

To access a modern command line interface developed by Microsoft, users can use the Command Prompt or PowerShell available on Windows operating systems. 

The Command Prompt provides a basic interface, while PowerShell offers more advanced features and functionality.

How To Use MS-DOS

At present, there are at least four different methods to utilize MS-DOS.

• Legacy systems: These are older IBM PC-compatible computers that are still in use today. Many of them still run some version of MS-DOS.

• Compatible OSes: There have been several operating systems published over the years that are compatible with MS-DOS. At least two open-source implementations of MS-DOS are still actively maintained, while other MS-DOS-compatible OSes are commercially available for use in embedded systems.

• MS-DOS emulators: These software programs virtually reconstruct the experience of working with MS-DOS. They allow users to run MS-DOS and MS-DOS-compatible programs on modern computer hardware and operating systems.

• Microsoft source code and binaries: Microsoft released the source code and binaries for two versions of MS-DOS to be used for education and experimentation. These resources allow people to learn how the operating system works and experiment with it in various ways.

MS-DOS operates through a command-line interface where users can input commands through the keyboard and view the system’s response in the form of the text output. A command prompt is displayed upon booting an MS-DOS system, and users can begin entering commands immediately. The input/output process is entirely text-based, with no graphical user interface available.

MS-DOS provides users with a set of standard commands that are implemented as part of the operating system. Additionally, users can also execute executable programs by typing in their file name in the command prompt. 

These commands and programs allow users to perform various tasks, such as managing files and directories, configuring system settings, and executing programs or applications.

Despite not having native support for a graphical user interface (GUI), MS-DOS can still run graphical programs if they are installed on a system disk or diskette. 

Users can input the command for a graphical program, and the program takes over the input and output devices. After the program ends, the control reverts back to MS-DOS, and the command prompt reappears. 

In other words, MS-DOS can act as a platform to launch and execute GUI-based applications, even if it does not have its own built-in GUI.

Compatible OSes for MS-DOS

During the peak of its popularity, MS-DOS served as a source of inspiration for other developers to create their own versions of the operating system for IBM PC-compatible computers. 

Some of these operating systems include:

DR-DOS

DR-DOS was an operating system developed by Digital Research as a competitor to MS-DOS and PC-DOS. It is no longer being distributed or supported and has been rebranded as Novell DOS and Caldera OpenDOS.

FreeDOS

FreeDOS is an open-source version of MS-DOS that is still actively developed, supported and used. It is compatible with most software developed for MS-DOS.

PTS-DOS

PTS-DOS is an MS-DOS clone developed in Russia that is still actively published. It is designed to be compatible with MS-DOS and can run most MS-DOS software.

ROM-DOS

ROM-DOS is an operating system used in embedded systems. It was first released in 1989 and is compatible with MS-DOS. Tuxera, a Finland-based embedded system software vendor, still sells ROM-DOS today.

For those interested in learning about MS-DOS, the open-source FreeDOS version is a popular choice among users. However, all of these operating systems are made to work on computers with Intel x86 processors.

Emulating MS-DOS on Modern Computers

Using a PC emulator, it is possible to run an MS-DOS clone or compatible operating system on a modern computer that is equipped with an Intel x86 processor. For example, FreeDOS can be installed on a virtual machine that emulates an old PC.

• DOSBox: A popular open-source MS-DOS emulator that allows users to run DOS-based games on modern operating systems such as Windows, macOS, and Linux. It is published under the GNU General Public License.

• vDos: It is another MS-DOS emulator that is designed specifically for the Windows operating system. It allows users to run legacy DOS software on their Windows computers and is available as freeware.

• Online MS-DOS emulator: James Friend, passionate about classic personal computing, offers an online emulator for PC-DOS. This emulator can be accessed through a web browser and requires no installation. Users can experience the MS-DOS environment directly from their web browser.

Using PC emulators is another way to run MS-DOS or compatible operating systems. For instance, a hobbyist, Hampa Hug, developed an emulator for the IBM PC model 5150 that allows users to experience working with a classic IBM PC on their modern computer.

Repository of Original MS-DOS Source Code

Microsoft has released the original source code and binaries for MS-DOS versions 1.25 and 2.0 on GitHub. The code was published in 2018 for those interested in exploring and experimenting with early PC operating systems.

The repository includes source code and binaries, which can be studied to gain insight into the inner workings of MS-DOS. This move by Microsoft has been welcomed by the tech community as it provides a unique opportunity to learn from the code that has been the foundation for modern computing.

History of MS-DOS Versions

The development of MS-DOS is closely tied to the rise of personal computing and the advent of IBM’s PC-DOS version and Microsoft Windows. MS-DOS has gone through various updates and improvements over the years. 

The timeline below outlines some significant milestones in the history of MS-DOS:

• In 1981, Microsoft purchased 86-DOS, a precursor to MS-DOS, from Seattle Computer Products and renamed it MS-DOS.

• In 1982, MS-DOS version 1.24 was supplied to IBM and released as PC-DOS 1.1.

• In 1983, MS-DOS 2.0 was introduced, with support for hard drives and subdirectories, to accompany IBM’s hard-drive-equipped computer, the IBM PC XT.

• In 1984, MS-DOS 3.1 was released in Europe, the first version of MS-DOS to have local area network support.

• In 1985, Microsoft released MS-DOS 3.2 specifically for IBM.

• In 1987, MS-DOS 3.3 was released with support for the 3.5-inch floppy disk format, which had a capacity of 1.44 Mb.

• In 1988, MS-DOS 4.01 was released with support for larger hard drives up to 2 Gb.

• In 1991, MS-DOS 5.0 was released, replacing GW-BASIC with Microsoft QBasic and providing support for dual-density 3.5-inch disks (2.88 Mb). This was the last version of MS-DOS developed with IBM’s PC-DOS.

• In 1992, MS-DOS 6.0 was introduced with disk management tools and backup and file transfer tools.

• In 1994, Microsoft released MS-DOS 6.22, which was the last version of standalone MS-DOS that the company developed.

• In 1995, Windows 95 was released, which includes a CLI implemented in MS-DOS 7.0 that enables users to launch MS-DOS applications from Windows.

• In 2000, MS-DOS 8.0 was included in Windows ME, the last version of MS-DOS that Microsoft released.

Features of DOS

The following are some unique characteristics that differentiate a disk operating system from other types of operating systems:

• Command-Line Interface: MS-DOS does not provide a Graphical User Interface (GUI) and does not support mouse input. All commands are entered in the text at the command-line prompt, making it a character-based interface system.

• File Management: MS-DOS provides a file system for organizing, reading, and writing files to disk storage. It can manage files, folders, and programs loading and execution. It can also control hardware devices such as disks and memory and allocate resources.

• Single-User Operating System: MS-DOS is a single-user operating system that performs various tasks to ensure the proper operation of systems. It does not support multi-user operating systems, and it is less secure, without any concept of user roles.

• File Allocation Table: MS-DOS uses a 16-bit file allocation table (FAT16), and a 16-bit interface is used to define the location of each file’s memory uniquely. These identifiers are stored in a tabular format with the name File Allocation Table.

• Lightweight: Due to its basic interface and limited features, MS-DOS is a very lightweight operating system. This makes it ideal for running on older or less powerful hardware systems, which is a significant advantage of MS-DOS. However, it is unsuitable for modern computing environments due to its limited functionality and security.

Limitations of MS-DOS

There are several limitations to using a disk operating system, including:

• Lack of built-in security measures: Disk operating systems like MS-DOS do not have built-in security features such as file ownership and permissions. This makes it more difficult to protect files from unauthorized access and maintain data integrity.

• No support for multiuser or multitasking environments: MS-DOS is a single-user operating system that can only run one program at a time. It cannot support multiple users or allow users to run multiple programs simultaneously.

• Single-user system that can only run one program at a time: MS-DOS can only run one program at a time, meaning users cannot multitask and run multiple programs simultaneously.

• Challenging command-line interface for beginners: The command-line interface of MS-DOS can be difficult for beginners to navigate. Users must enter text commands to execute programs and perform other tasks, and they must remember specific commands and syntax to use the system effectively.

• Limited memory management capabilities: MS-DOS has limited memory management capabilities, meaning it cannot effectively manage large amounts of memory or allocate resources efficiently.

• Can only address up to 640KB of memory: MS-DOS is limited in its ability to address memory, with a maximum limit of 640 KB. This means that the system can only access a certain amount of memory, which can be a limitation for running more complex programs or processes.

Popular MS-DOS Commands

MS-DOS commands are built-in functions in the operating system that can be executed by typing them into the command prompt. The number of available commands may vary depending on the version of MS-DOS being used, but typically there are around 100 different commands to choose from.

Despite not being part of the OS, other executable programs like DOS commands can be input at the command line. The following two are examples of executable programs:

Batch files in MS-DOS

Batch files are text files that contain a series of MS-DOS commands and can also include application programs. They are often used to automate repetitive tasks or to execute a series of commands in a specific order. Batch files can also use programming constructs such as loops and conditional statements to make decisions based on input or output from previous commands. 

Application Programs

Application programs are files containing machine-readable code that a computer can execute. They are created by compiling source code into a binary executable format that the computer’s processor can understand.

Early PC users considered working at the command line an essential skill. While many users primarily worked with software applications like word processors, spreadsheets, and file managers, having proficiency in the command line was still an important skill to have.

Some of the commonly used MS-DOS commands are listed below: