Updated February 10, 2017
Command Line Interface
MS-DOS uses a command line interface, forcing the user to input commands at a prompt. The command set for DOS is limited. It consists mainly of navigation and file manipulation commands. Most complex operations are handled by the programs themselves. Since users have to enter commands in sequence, they could create batch files, which are text files listing a series of commands that the OS would execute in order. One common example of this is AUTOEXEC.BAT, a batch file that the OS runs on first boot and contains commands to set up the computing environment.
Single Tasks
Because Microsoft intended MS-DOS to run on early PCs without much in the way of RAM, MS-DOS features no ability for programs to multitask. When the user runs a program, that program consumes system resources until it stops, and then another program may access memory. Certain types of programs called TSRs, for Terminate and Stay Resident, can park themselves in memory, but these programs are vulnerable to memory overlap and frequently crashed. The first versions of Windows introduced true multitasking to PCs.
Filenames
One distinctive characteristic of MS-DOS is its “8+3” file naming system. File names are limited to eight characters, with a three-character suffix denoting the type of file. For instance, TXT and DOC denote text files, while COM and EXE indicate executables and SYS is reserved for system files. Windows has since done away with the eight-character limit, although file suffixes still indicate to the OS how to handle each type of file, and many of the original suffixes from the early days of MS-DOS still exist.
Drive Letters
Another prominent characteristic of MS-DOS is its use of letters to refer to drives. Typically, A and B designate floppy drives, while C and anything later in the alphabet refers to hard drives or optical drives. Users have the ability to map any drive letter they wish, although typically they would assign them in alphabetical order. Today, Windows still uses drive letters, and still reserves A and B by default, despite the fact that modern PCs typically do not contain floppy drives. Writer Bio
