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 single processor between several independent jobs. The first multitasking operating systems were designed in the early 1960s.

Under "cooperative multitasking" the running task decides when 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 has run for a fixed period known as a "time-slice". In both cases the scheduler is responsible for selecting the next task to run and (re)starting it.

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

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

Multitasking introduces overheads because the processor spends some time in choosing the next job to run and in saving and restoring tasks' state, but it reduces the worst-case time from job submission to completion compared with a simple batch system where each job must finish before the next one starts. Multitasking also means that while one task is waiting for some external event, the CPU to do useful work on other tasks.

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

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

Multithreading is a kind of multitasking with low overheads and no protection of tasks from each other, all threads share the same memory.

This article is provided by FOLDOC - Free Online Dictionary of Computing (foldoc.org)

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.

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References in periodicals archive

People will choose to multitask. But we should, at the very least, be fully aware of how that choice affects us and the potential consequences for ourselves and others.

The high price of multitasking

(2014) in which adolescents who multitask more frequently reported more problems staying focused, inhibiting inappropriate behaviour, and switching effectively between tasks.

Media multitasking impact in homework, executive function and academic performance in Spanish adolescents

For example, it has been found that people who are in the possession of screens such as a computer, laptop, and television are more likely to media multitask (Foehr, 2006).

Audience, Media, and Cultural Factors as Predictors of Multiscreen Use: A Comparative Study of the Netherlands and the United States

Furthermore, the focus group results give us additional insight into how people might apply the "skill" necessary to multitask "well".

An integrated perspective of multitasking and multiple team membership

Next, I try very hard not to multitask and to be more mindful and focused on the most important task at hand.

More time management tips for busy people

First of all, according to Nass, we don't really multitask because our processing isn't simultaneous, but rather sequential.

Excuse me, I've got to take this

In contrast to everything else in your life, the more you multitask, the worse you are at it."

Multitasking: a lie we tell ourselves

A significant interaction between IM condition and reading passage difficulty was expected, with the greatest decrease in performance accuracy (i.e., reading comprehension) in those participants in the IM condition whose multitask involved the difficult reading task (hypothesis 2).

The effects of instant messaging and task difficulty on reading comprehension

The fantasy that is promoted as fact, that humans can multitask effectively over a lifetime, is creating generations of focus-lessness.

AT&T's dizzying tizzy

A University of Utah study published earlier this year at PLOS ONE measured the ability of undergraduate psychology students to multitask, along with their perceived ability to do so.

If you think you can, don't!

Dave Crenshaw advises using what he calls 'switch busters' to limit the temptation to multitask. These include turning off your phone at appropriate times such as when in meetings, turning off your monitor when you're on the phone, and scheduling appointments with the people who consistently interrupt you so they can ask their questions during the allocated time.

Hazards of multi-tasking

Of course, no one should multitask by driving a vehicle while texting on a cell phone.

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