An Operating Systems Vade Mecum

Glossary 337Finalization. Action taken when a resource is released to put it in the proper state.First fit. (1) A space-allocation policy that accepts the first region of space that has adequatecontents. (2) A resource-allocation policy aimed at reducing starvation by grantingresources, if safe, to processes that have been waiting longer. (See Best fit.)Flag. A parameter in a command that specifies an optional behavior of the process thatthe command invokes.Flat. A file structure is flat if all file names are in the same directory. Also called onelevel.Foreground. An interactive process, usually given higher priority than the noninteractivebackground processes. (Opposite of Background.)Format. (1) To establish the structure of a disk pack, laying out sector boundaries. (2)To establish the disk structures for a file system.Frame. (1) A region on magnetic tape that is 1 bit long and (usually) 9 bits wide. (2) Aunit of transmission that is short enough so that the sender and receiver clocks remainsynchronized during the transmission.Free port. A communication port with many writers and many readers.Full duplex. A kind of communication line where data may travel in both directionssimultaneously. (See Half duplex and Simplex.)Full name. The name of a file that includes its path name and its local name.Gateway. A computer on two networks that can transfer messages from one to the other.Global. A global page replacement policy selects pages to discard from any process.(See Local and Pool.)Group identifier. A number associated with all the processes and files created for a particulargroup of users. This number is used for accounting and protection purposes. (SeeUser identifier.)Guard. A procedure exported from a monitor. Guards are mutually exclusive.Half duplex. A kind of communication line where data travels in either direction, butonly in one direction at a time. (See Full duplex and Simplex.)Hamming distance. The number of bit positions at which two strings differ.Handler. A program that responds to interrupts.Hardware. The bare computer, including its main store, the devices attached to it, andits central processing unit.Header. (1) The prefix on a transmission frame, used to synchronize the sender and thereceiver. (2) More generally, extra information placed in a message by a level oftransmission protocol.Hierarchical allocation. A policy for resource allocation under which a process mayonly request resources that have a higher level than any resource it currently holds.