multitasking

mul·ti·task·ing

M0480350 (mŭl′tē-tăs′kĭng, -tī-)n.1. The concurrent operation by one central processing unit of two or more processes.2. The engaging in more than one activity at the same time or serially, switching one's attention back and forth from one activity to another.

mul′ti·task′ v.

multitasking

(ˈmʌltɪˌtɑːskɪŋ) n1. (Computer Science) computing the execution of various diverse tasks simultaneously2. the carrying out of two or more tasks at the same time by one person

mul•ti•task•ing

(ˌmʌl tiˈtæs kɪŋ, -ˈtɑ skɪŋ, ˌmʌl taɪ-)

n. Computers. the concurrent execution of two or more jobs by a single CPU.

Translations

Multitasking

multitasking

[¦məl·tē′task·iŋ] (computer science) The simultaneous execution of two or more programs by a single central processing unit.

multitasking

(computer, parallel)(Or "multi-tasking", "multiprogramming","concurrent processing", "concurrency", "process scheduling")A technique used in an operating system for sharing a singleprocessor between several independent jobs. The firstmultitasking operating systems were designed in the early1960s.

Under "cooperative multitasking" the running task decideswhen to give up the CPU and under "pre-emptive multitasking"(probably more common) a system process called the"scheduler" suspends the currently running task after it hasrun for a fixed period known as a "time-slice". In bothcases the scheduler is responsible for selecting the next taskto run and (re)starting it.

The running task may relinquish control voluntarily even in apre-emptive system if it is waiting for some external event.In either system a task may be suspended prematurely if ahardware interrupt occurs, especially if a higher prioritytask was waiting for this event and has therefore becomerunnable.

The scheduling algorithm used by the scheduler determineswhich task will run next. Some common examples areround-robin scheduling, priority scheduling, shortest job first and guaranteed scheduling.

Multitasking introduces overheads because the processorspends some time in choosing the next job to run and in savingand restoring tasks' state, but it reduces the worst-case timefrom job submission to completion compared with a simplebatch system where each job must finish before the next onestarts. Multitasking also means that while one task iswaiting for some external event, the CPU to do useful workon other tasks.

A multitasking operating system should provide some degree ofprotection of one task from another to prevent tasks frominteracting in unexpected ways such as accidentally modifyingthe contents of each other's memory areas.

The jobs in a multitasking system may belong to one or manyusers. This is distinct from parallel processing where oneuser runs several tasks on several processors. Time-sharingis almost synonymous but implies that there is more than oneuser.

Multithreading is a kind of multitasking with lowoverheads and no protection of tasks from each other, allthreads share the same memory.

multitasking

The running of two or more programs in one computer at the same time. The number of programs that can be effectively multitasked depends on the sophistication of the operating system, the speed of the CPU and the speeds and capacities of memory (RAM) and storage. See preemptive multitasking.

Input/Output vs. Processing
Programs can run simultaneously in the computer because of the difference between I/O and processing speed. While one program is waiting for input, instructions in another can be executed. During the milliseconds one program waits for data to be read from storage, millions of instructions in another program can be executed. Thousands of instructions can be executed in one program between each keystroke in another program.

Channels and Multicore
In mainframe architectures, multiple I/O channels allow for simultaneous I/O operations to take place. Multiple streams of data, sometimes hundreds, are being read and written at the exact same time. In a multicore CPU, one program can be running in one core while another is multitasked in another core, and so on (see multicore).

Multitasking May Be Just Task Switching
Very often, people think multitasking is occurring when what is really taking place is "task switching." Multitasking implies simultaneous operation; for example, while the user interacts with the program on screen, a program in the background is processing data.

However, when several programs reside in memory (RAM) and do nothing but wait to be "front and center" again, the user is switching between programs (between apps, between tasks). See task switching.

A Note on Ancient Terminology
In the 1960s, the days of only mainframes, multitasking was called "multiprogramming," and multitasking meant "multithreading." See multithreading.

单词	multitasking
释义	multitasking mul·ti·task·ing M0480350 (mŭl′tē-tăs′kĭng, -tī-)n.1. The concurrent operation by one central processing unit of two or more processes.2. The engaging in more than one activity at the same time or serially, switching one's attention back and forth from one activity to another. mul′ti·task′ v. multitasking (ˈmʌltɪˌtɑːskɪŋ) n1. (Computer Science) computing the execution of various diverse tasks simultaneously2. the carrying out of two or more tasks at the same time by one person mul•ti•task•ing (ˌmʌl tiˈtæs kɪŋ, -ˈtɑ skɪŋ, ˌmʌl taɪ-) n. Computers. the concurrent execution of two or more jobs by a single CPU. Translations Multitasking multitasking multitasking [¦məl·tē′task·iŋ] (computer science) The simultaneous execution of two or more programs by a single central processing unit. multitasking (computer, parallel)(Or "multi-tasking", "multiprogramming","concurrent processing", "concurrency", "process scheduling")A technique used in an operating system for sharing a singleprocessor between several independent jobs. The firstmultitasking operating systems were designed in the early1960s. Under "cooperative multitasking" the running task decideswhen to give up the CPU and under "pre-emptive multitasking"(probably more common) a system process called the"scheduler" suspends the currently running task after it hasrun for a fixed period known as a "time-slice". In bothcases the scheduler is responsible for selecting the next taskto run and (re)starting it. The running task may relinquish control voluntarily even in apre-emptive system if it is waiting for some external event.In either system a task may be suspended prematurely if ahardware interrupt occurs, especially if a higher prioritytask was waiting for this event and has therefore becomerunnable. The scheduling algorithm used by the scheduler determineswhich task will run next. Some common examples areround-robin scheduling, priority scheduling, shortest job first and guaranteed scheduling. Multitasking introduces overheads because the processorspends some time in choosing the next job to run and in savingand restoring tasks' state, but it reduces the worst-case timefrom job submission to completion compared with a simplebatch system where each job must finish before the next onestarts. Multitasking also means that while one task iswaiting for some external event, the CPU to do useful workon other tasks. A multitasking operating system should provide some degree ofprotection of one task from another to prevent tasks frominteracting in unexpected ways such as accidentally modifyingthe contents of each other's memory areas. The jobs in a multitasking system may belong to one or manyusers. This is distinct from parallel processing where oneuser runs several tasks on several processors. Time-sharingis almost synonymous but implies that there is more than oneuser. Multithreading is a kind of multitasking with lowoverheads and no protection of tasks from each other, allthreads share the same memory. multitasking The running of two or more programs in one computer at the same time. The number of programs that can be effectively multitasked depends on the sophistication of the operating system, the speed of the CPU and the speeds and capacities of memory (RAM) and storage. See preemptive multitasking. Input/Output vs. Processing Programs can run simultaneously in the computer because of the difference between I/O and processing speed. While one program is waiting for input, instructions in another can be executed. During the milliseconds one program waits for data to be read from storage, millions of instructions in another program can be executed. Thousands of instructions can be executed in one program between each keystroke in another program. Channels and Multicore In mainframe architectures, multiple I/O channels allow for simultaneous I/O operations to take place. Multiple streams of data, sometimes hundreds, are being read and written at the exact same time. In a multicore CPU, one program can be running in one core while another is multitasked in another core, and so on (see multicore). Multitasking May Be Just Task Switching Very often, people think multitasking is occurring when what is really taking place is "task switching." Multitasking implies simultaneous operation; for example, while the user interacts with the program on screen, a program in the background is processing data. However, when several programs reside in memory (RAM) and do nothing but wait to be "front and center" again, the user is switching between programs (between apps, between tasks). See task switching. A Note on Ancient Terminology In the 1960s, the days of only mainframes, multitasking was called "multiprogramming," and multitasking meant "multithreading." See multithreading. multitasking multitasking Informatics The ability of an operating system to simultaneously run multiple programs–eg, graphics, spreadsheets, word processing or formats of software–eg, coding, compiling, testing Multitasking Performing multiple duties or taking on multiple responsibilities and roles simultaneously.Mentioned in: Myers-Briggs Type Indicator LegalSeeConcurrentThesaurusSeeconcurrency
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