DOS (Disk Operating System) is a single-tasking, single-user command-line operating system.
Microsoft created the original version in 1981 for IBM and was called PC-DOS. Microsoft then ported and sold the system to IBM-PC compatible computers manufactured by others than IBM under the name of the Microsoft Disk Operating System (MS-DOS).
This version was the most popular OS at the time. In addition to the original versions of Microsoft/IBM code, there are other versions of DOS, more or less compatible with MS-DOS/PC-DOS such as DR-DOS and FreeDOS. This was possible due to the simplicity of the system but also due to its origin in another operating system, called CP/M.
Until the advent of Windows 95, it was the most popular operating system on x86 architecture.
DOS systems were designed considering the performance of micro-computers in the early 1980s. From the perspective of current users, it is extremely limited, but for the standards of the time, it was a system comparable to the competition: it used a relatively light set of commands (for example copy compared to PIP in CP / M), it could address a maximum of 640 KB of RAM (in an era when microcomputers only had 32 KB of RAM), provides the user interface with disks in an interactive way and, most importantly, consumes a small number of resources.
MS-DOS (short for Microsoft Disk Operating System) is an operating system marketed by Microsoft.
It was the most widely used operating system in the DOS family and dominated PC operating systems in the 1980s.
It was based on the Intel 8086 family of microprocessors, especially the IBM PC and compatible.
It has been gradually replaced by operating systems that provide a graphical interface, especially the various generations of the Microsoft Windows operating system.
It was originally known as QDOS (Quick and Dirty Operating System) and 86-DOS. MS-DOS was originally launched in 1981 and had eight major versions released before Microsoft stopped development in 2000.
It was a key product for Microsoft’s growth due to the various programming languages the company created for software development companies, provided significant revenue to the company and marketing resources.
It was the operating system on which the first versions of Windows were run as a graphical interface.
Initially, MS-DOS was intended to be an operating system that could work on any processor family of 8086. Each computer had to have its own hardware configuration and version of MS-DOS.
The biggest need for hardware resources was video games. Then the target became IBM compatible architecture. Soon, all the computers in the 8086 families were imitating IBM hardware, and a single version of MS-DOS was available for the entire market.
While MS-DOS was used by IBM PC clones, true IBM computers used PC-DOS, a modified version of MS-DOS.
Moreover, the dependence of IBM compatible hardware caused major problems for the industry when the original design was changed. For example, the original design could not support more than 640 KB of RAM. Manufacturers have begun to develop complicated schemes for accessing additional memory. This would not have been a limitation if the original idea of MS-DOS interfacing with the hardware had not suffered.