MS-DOS: A Brief Introduction

A Quick and Dirty History

When IBM launched its revolutionary personal computer, the IBM PC, in August 1981, it came complete with a 16-bit operating system from Microsoft, MS-DOS 1.0. This was Microsoft’s first operating system, and it also became the first widely used operating system for the IBM PC and its clones.

MS-DOS 1.0 was actually a renamed version of QDOS (Quick and Dirty Operating System), which Microsoft bought from a Seattle company, appropriately named Seattle Computer Products, in July 1981. QDOS had been developed as a clone of the CP/M eight-bit operating system in order to provide compatibility with the popular business applications of the day such as WordStar and dBase. CP/M (Control Program for Microcomputers) was written by Gary Kildall of Digital Research several years earlier and had become the first operating system for microcomputers in general use.

Today, MS-DOS is no longer used; however, the command shell, more commonly known as the Windows command line is still used by many users. The picture to the right is an example of what an MS-DOS window more appropriately referred to as the Windows command line looks like running under Microsoft Windows.

Most computer users are only familiar with how to navigate Microsoft Windows using the mouse. Unlike Windows, MS-DOS is a command-line and is navigated by using MS-DOS commands. For example, if you wanted to see all the files in a folder in Windows you would double-click the folder to open the folder in Windows Explorer. In MS-DOS, to view that same folder you would navigate to the folder using the command and then list the files in that folder using the dir command.

Microsoft initially kept the IBM deal a secret from Seattle Computer Products. And in what was to become another extremely fortuitous move, Bill Gates, the not uncontroversial co-founder of Microsoft, persuaded IBM to let his company retain marketing rights for the operating system separately from the IBM PC project. Microsoft renamed it PC-DOS (the IBM version) and MS-DOS (the Microsoft version). The two versions were initially nearly identical, but they eventually diverged.

The acronym DOS was not new even then. It had originally been used by IBM in the 1960s in the name of an operating system (i.e., DOS/360) for its System/360 computer. At that time the use of disks for storing the operating system and data was considered cutting-edge technology.

Until its acquisition of QDOS, Microsoft had been mainly a vendor of computer programming languages. Gates and co-founder Paul Allen had written Microsoft BASIC and were selling it on disks and tape mostly to PC hobbyists.

DOS Commands

MS-DOS has a relatively small number of commands and an even smaller number of commonly used ones. Moreover, these commands are generally inflexible because, in contrast to Linux and other Unix-like operating systems, they are designed to accommodate few options or arguments (i.e., values that can be passed to the commands).

Some of the most common commands are as follows (corresponding commands on Unix-like operating systems are shown in parenthesis):

CD – changes the current directory (cd) 
COPY – copies a file (cp
DEL – deletes a file (rm
DIR – lists directory contents (ls) 
EDIT – starts an editor to create or edit plain text files (vi, vim, ed, joe) 
FORMAT – Formats a disk to accept DOS files (format) 
HELP – displays information about a command (man, info) 
MKDIR – creates a new directory (mkdir
RD – removes a directory (rmdir
REN – Renames a file (mv
TYPE – displays contents of a file on the screen (more, cat)

comparison between MS-DOS and Linux

MS-DOS and Linux have much in common, primarily because MS-DOS copied many ideas from UNIX. However, there are some very fundamental differences, including:

(1) Linux is a full-fledged multiuser, multitasking operating system, whereas MS-DOS is a single-user, single-tasking operating system.

(2) MS-DOS does not have built-in security concepts such as file-ownership and permissions, which are fundamental to Linux.

(3) Linux has an inverted tree-like filesystem in which all directories and files branch from a single directory, i.e., the root directory, and its subdirectories. MS-DOS can have multiple, independent root directories, such as A:, C:, D:, etc.

(4) Linux uses forward slashes “/” to separate directories, whereas MS-DOS uses backslashes “\” for the same purpose.

(5) Linux filenames can contain up to 255 characters. MS-DOS filenames are limited to eight characters plus a three-character extension and have restrictions on allowable characters. Also, filenames are case-sensitive in Linux, whereas they are not in MS-DOS.

(6) Linux has a vastly richer command set than does MS-DOS, with a much greater number of commands and individual commands having greater power, flexibility, and ease of use. Commands are case-sensitive in Linux, but they are not in MS-DOS.

(7) Although Linux and MS-DOS both have pipes and input/output redirection, the MS-DOS pipes use a completely different — and inferior — implementation.

(8) MS-DOS is not sufficiently flexible and efficient to serve as a base for a high quality, general-purpose GUI (and thus it had to be abandoned by Microsoft). In sharp contrast, Linux is an excellent base for a GUI (and it is used as a base for the X Window System, which is extremely configurable and whose already excellent performance continues to improve).


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