In
computer science
Computer science is the study of computation, automation, and information. Computer science spans theoretical disciplines (such as algorithms, theory of computation, information theory, and automation) to Applied science, practical discipli ...
, a command queue is a
queue __NOTOC__
Queue () may refer to:
* Queue area, or queue, a line or area where people wait for goods or services
Arts, entertainment, and media
*''ACM Queue'', a computer magazine
* ''The Queue'' (Sorokin novel), a 1983 novel by Russian author ...
for enabling the delay of command execution, either in order of
priority, on a
first-in first-out basis, or in any order that serves the current purpose. Instead of waiting for each command to be executed before sending the next one, the program just puts all the commands in the queue and goes on doing other things while the queue is processed by the
operating system
An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs.
Time-sharing operating systems schedule tasks for efficient use of the system and may also in ...
.
This delegation not only frees the program from handling the queue but also allows a more optimized execution in some situations. For instance, when handling multiple requests from several users, a network server's hard drive can reorder all the requests in its queue using, for instance, the
elevator algorithm
The elevator algorithm (also 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 elevat ...
to minimize the 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 dri ...
(NCQ) in
Serial ATA
SATA (Serial AT Attachment) is a computer bus interface that connects 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 (PATA) standard t ...
(SATA)
*
Tagged Command Queuing Tagged Command Queuing (TCQ) is a technology built into certain ATA and SCSIin the form of Parallel SCSI, Serial attached SCSI, and Fibre Channel drives hard drives. It allows the operating system to send multiple read and write requests to a ha ...
(TCQ) in
Parallel ATA
Parallel ATA (PATA), originally , also known as 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 CD or DVD drives. The connection ...
and
SCSI
Small Computer System Interface (SCSI, ) is a set of standards for physically connecting and transferring data between computers and peripheral devices. The SCSI standards define commands, protocols, electrical, optical and logical interface ...
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 mode is a generic electronics term referring to any situation in which a device is transmitting data repeatedly without going through all the steps required to transmit each piece of data in a separate transaction. Advantages
The main advantag ...
*
Command pattern
In object-oriented programming, the command pattern is a behavioral design pattern in which an object is used to encapsulate all information needed to perform an action or trigger an event at a later time. This information includes the method name ...
*
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 s ...
*
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'' ...
References
Job scheduling
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