Control block

In computing, a control block is an area of memory or disk which contains a group of related data "used for identification and control purposes".

Computer operating systems, subsystems, and applications use control blocks to consolidate information regarding system and resource status. An operating system will have a control block which tracks the status of running programs. Examples of this are the process control block, thread control block, Task Control Block, or Service Request Blocks. Control blocks, which may be called called Unit Control Blocks, hold the status of all devices known to the system. Opened files are identified by control blocks which may be called File Control Blocks or Data Control Blocks. Operating systems or applications may manage memory using control blocks. For example IBM OS/360 MVT maintains subpools of storage for different purposes, which are tracked by control blocks.

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