loads on top of the operating system and offers users commands that lets them access the OS. Strictly speaking, the shell is an input utility that offers access to the operating system. Technically speaking, the shell, being a separate program, is not a part of the OS at all. In the UNIX world a number of shells are available, among them the Korn shell, the C-shell, the Bourne shell and the Bourne Again shell (yes, really). In DOS, the standard shell is COMMAND.COM, again nothing more than a program. As different versions of command.com came with different versions of DOS, each added new commands and new things that could be done by the user. For example, DOS 4's COMMAND.COM added theP switch to DEL to verify each deletion, and DOS 5's COMMAND.COM provided the ability to sort the output of the DIR command. HISTORY An acronym for disk operating system, the term DOS can refer to any operating system, but is most often used as shorthand for MS-DOS. Originally developed by Microsoft for IBM, MS-DOS was the standard operating system for IB
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