batch file
In DOS, OS/2, and Microsoft Windows, a batch file is a text file containing a series of commands intended to be executed by the command interpreter. When a batch file is run, the shell program (usually COMMAND.COM or cmd.exe) reads the file and executes its commands, normally line-by-line. Batch files are useful for running a sequence of executables automatically and are often used by system administrators to automate tedious processes.
DOS batch files have the filename extension .bat (or .BAT because file names are case insensitive in DOS, Windows and OS/2). Batch files for other environments may have different extensions, e.g. .cmd in Windows NT and OS/2, or .btm in 4DOS and related shells. The Windows 9x family only recognizes the .bat extension.
History
The command interpreters provide two distinct modes of work: interactive mode (in which the user types commands at a command prompt which are then executed immediately) and batch mode (which executes a predefined sequence of commands). The original concepts for both modes draw ideas from Unix shells, as well as other text-based command line interfaces from the early 1980s such as CP/M which in turn took much of their inspiration from TOPS-10 and TOPS-20 from Digital Equipment Corporation.
Microsoft DOS and Windows batch programming has evolved along with the product releases of these operating systems. Although a batch file is analogous to a shell in Unix-like operating systems, the limited syntax and commands available means it is less suited for general-purpose programming. These limitations led to various non-Microsoft interpreters to provide enhanced syntax by providing "enhancement" commands such as those in the Norton Utilities (like the BE or Batch Enhancer) and in 1989 the replacement shell 4DOS and later 4NT.
The batch program interpreter for MS-DOS and compatible DOSes is COMMAND.COM. Batch programs for MS-DOS are composed of a relatively simple set of commands interpreted directly by COMMAND.COM (internal commands), and utilities that exist as separate executables (external commands). The most commonly used batch file was AUTOEXEC.BAT. If present, it was automatically executed during the booting process.
The evolution of this branch of batch programming proceeded through the releases of MS-DOS, and continued with the early versions of Microsoft Windows through to Windows 95, Windows 98, and finally Windows Me, which remained based on MS-DOS.
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