File control block

<operating system> (FCB) An MS-DOS data structure that stores information about an open file.

The number of FCBs is configured in CONFIG.SYS with a command

FCBS=x,y

where x (between 1 and 255 inclusive, default 4) specifies the number of file control blocks to allocate and therefore the number of files that MS-DOS can have open at one time.

y (not needed from DOS 5.0 onward) specifies the number of files to be closed automatically if all x are in use.

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file File Allocation Table File Attach File Composition file compression	CONFIG.SYS FCB file control block	file descriptor file descriptor leak file extension FileMaker FileMaker, Inc.