In
computer science
Computer science is the study of computation, information, and automation. Computer science spans Theoretical computer science, theoretical disciplines (such as algorithms, theory of computation, and information theory) to Applied science, ...
, a command queue is a
queue that determines when a command is executed, usually by order of
priority or on a
first-in first-out basis. Instead of waiting for each command to be executed before sending the next one, a program will put all its commands in the command queue, freeing it to perform other functions while the queue is processed by the
operating system
An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs.
Time-sharing operating systems scheduler (computing), schedule tasks for ...
.
This delegation not only frees the program from handling the queue but can also help optimize execution. For instance, when handling multiple requests from several users, a network server's hard drive can reorder the requests in its queue using the
elevator algorithm
The elevator algorithm, or SCAN, is a hard disk, disk-I/O scheduling, scheduling algorithm to determine the motion of the disk's arm and head in servicing read and write requests.
This algorithm is named after the behavior of a building elevator ...
, which minimizes mechanical movement.
Examples
*
Native Command Queuing
In computing, Native Command Queuing (NCQ) is an extension of the Serial ATA protocol allowing hard disk drives to internally optimize the order in which received read and write commands are executed. This can reduce the amount of unnecessary driv ...
(NCQ) in
Serial ATA
SATA (Serial AT Attachment) is a computer bus interface that connects host adapter, host bus adapters to mass storage devices such as hard disk drives, optical drives, and solid-state drives. Serial ATA succeeded the earlier Parallel ATA (PAT ...
(SATA)
*
Tagged Command Queuing (TCQ) in
Parallel ATA
Parallel ATA (PATA), originally , also known as Integrated Drive Electronics (IDE), is a standard interface designed for IBM PC-compatible computers. It was first developed by Western Digital and Compaq in 1986 for compatible hard drives and C ...
and
SCSI
Small Computer System Interface (SCSI, ) is a set of standards for physically connecting and transferring data between computers and peripheral devices, best known for its use with storage devices such as hard disk drives. SCSI was introduced ...
See also
*
Batch processing
Computerized batch processing is a method of running software programs called jobs in batches automatically. While users are required to submit the jobs, no other interaction by the user is required to process the batch. Batches may automatically ...
*
Burst mode (computing)
Burst may refer to:
*Burst mode (disambiguation), a mode of operation where events occur in rapid succession
**Burst transmission
Burst may refer to:
*Burst mode (disambiguation), a mode of operation where events occur in rapid succession
**Burst ...
*
Command pattern
In object-oriented programming, the command pattern is a Behavioral pattern, behavioral Design pattern (computer science), design pattern in which an object is used to Information hiding, encapsulate all information needed to perform an action or ...
*
Job queue
In system software, a job queue ( batch queue, input queue), is a data structure maintained by job scheduler software containing jobs to run.
Users submit their programs that they want executed, "jobs", to the queue for batch processing.
The ...
*
Job scheduler
A job scheduler is a computer application for controlling unattended background program execution of jobs. This is commonly called batch scheduling, as execution of non-interactive jobs is often called batch processing, though traditional ''job ...
Job scheduling
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