How Multitasking Feature Works in Operating Systems?
The more modern term multitasking includes the idea of multiprogramming but extends the concept to include the ability to run different parts of the same also known as threads simultaneously. The basic idea is that most programs can be treated as a sequence of smaller elements called tasks. Sometimes these tasks must be executed and completed in order, one at a time. For example, task 2, say, may need the results from task1 before it can proceed. On other occasions, some or all of the tasks in the program can be usefully tackled independently, without regard to the other tasks that are running. And, of course, you will encounter mixed situations where task1, task2, and task3 can be run independently, but task 4 must await their completion.
Another element in the jigsaw is that many peripherals, such as tape and disk drives, can also operate independently. An I/O task such as reading from a disk can be triggered by a system call in program A and left to run independently while the operating system prepares to run another task or program. The operating system scans its table of suspended jobs and determines which of those that are “runnable” phase has the highest priority, say program B. This context of program A is then stored together with a flag indicating its wait status like waiting for a disk read. The previously saved context of program B is then restored and program B starts executing. But how will the suspended program A ever get restarted? Well, the I/O device needs to signal that its operation is complete, and this is done by a device interrupt.
Device interrupts are messages that system peripherals send to the CPU, telling it that they need its attention. For example, when you press a key on your keyboard, the keyboard stores the value of the keystroke and sends and interrupts to the CPU, telling it that it has data waiting for it. As the name implies, an interrupt can occur at any time, and the kernel must take note of it even if no immediate restart of program A is possible. The kernel’s reaction to the interrupt, in this case, would be to change the status of program A from waiting for disk read to the “runnable” phase. This restores program A as a candidate for execution, and eventually, depending on its relative priority, program A will regain its place in the sun.
Peeling the onion layers of nested complex business processes is the key to a global vision and great faith. Fortunately, Unix and Linux are a few simple commands, like so many programs running as you want and you can track your progress. Some Unix and Linux using a GUI to a very good combination. In this interface, you can run multiple programs without any command-line. Currently, there are some versions of Linux, the graphical user interface like Windows. You know that people feel comfortable in Windows, and if people think the same type of graphical user interface on Linux, you feel comfortable with it. The modern definition encompasses the idea of multi-programming tasks, but the concept extends the ability to use different parts called threads at a time. The basic idea is that most programs cannot be treated as a series of small elements called tasks. Sometimes these tasks and completed sequentially, one at a time. For example, Task 2, for example, before the results of Task 1 continues. Another time, the entire program is useful for solving problems, regardless of the task. And of course, you can handle situations where a common task, Task3 Task2 and can be used alone but must await the completion of four tasks.
Another piece of the puzzle is that many devices such as tape and disk drives can operate independently. Task I / O can be read as a system disk to the program is designed to work independently and to the left, while the operating system is ready to perform another task or program. The operating system and the suspension of the table list the tasks that are “executable” phase, which is the highest priority, for example, B. In this connection, the program awaits the identification number of the Program on standby to disk and keeps reading. The program is stored in the restored B & B, the program starts. But when the program hangs after reboot? Well, the device I / O should be noted that the process is complete and that by breaking the device.
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