The MS-DOS File System
In MS-DOS, the file was the primary unit of data storage on the computer. It allowed the system to distinguish a single collection of information from another. Files were organized into directories. File and directory names were up to eight characters long, were not case-sensitive and could have a three-letter extension following a period. Several file extensions were universally used. These naming extensions have been carried over into the Windows environment.
| Common File Extensions | |
| Extension | Description |
| .exe | Files with this extension are the executable file of programs
or applications. |
| .com | Files with this extension are the command files of programs
or applications. |
| .sys | Files with this extension are system files that are used to
define and configure options. |
| .bat | Files with this extension are batch files. These are text files
that can be run to execute a series of commands or launch programs. |
| .txt | Files with this extension are text files consisting of plain ASCII data. |
| .doc | Files with this extension are document files created with word processors and include file text with formatting. |
| .drv | Files with this extension are driver files that are used to configure hardware devices. |