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Operating Systems By: Lecturer Raoof Talal 1 Process Concept
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Bog'liq 5 2020 03 26!09 57 40 PM 7-maruza, Asal, 2021 Itimoiy ish 16 aIshchi Dastur — копия 10 — копия, 17-Amaliy mashgulot, 6-ma\'ruza. Furyе qatоrining yaqinlashishi, Antarktda, Magnitomexanik hodisalar, 1.8, Abdulahad Muhammadjonov. Qadimgi Buxoro (2001), yillik hisobot rasmsiz, Oqsillar, Stajirovka rejasi 2-илова, file (2), Ekinlarni sug\'orish asoslari (Z.Artukmetov), Sanoq sistemalar Chapter 5
Operating Systems
By: Lecturer Raoof Talal
5.1 Process Concept
A question that arises in discussing operating systems involves what to call all the CPU activities. A batch system executes jobs, whereas a time-shared system has user programs, or tasks. Even on a single-user system such as Microsoft Windows, a user may be able to run several programs at one time: a word processor, a web browser, and an e-mail package. Even if the user can execute only one program at a time, the operating system may need to support its own internal programmed activities, such as memory management. In many respects, all these activities are similar, so we call all of them processes. The terms job and process are used almost interchangeably in this text.
5.1.1 The Process
Informally, as mentioned earlier, a process is a program in execution. A process is more than the program code, which is sometimes known as the text section.
- A process generally also includes the process stack, which contains temporary data,
- and a data section, which contains global variables.
- A process may also include a heap, which is memory that is dynamically allocated during process run time. The structure of a process in memory is shown in Figure 5.1.
We emphasize that a program by itself is not a process; a program is a passive entity, such as a file containing a list of instructions stored on disk (often called an executable file), whereas a process is an active entity, with a program counter specifying the next instruction to execute and a set of associated resources.
A program becomes a process when an executable file is loaded into memory.
5.1.2 Process State
As a process executes, it changes state. The state of a process is defined in part by the current activity of that process. Each process may be in one of the following states:
- New: The process is being created.
- Running: Instructions are being executed.
- Waiting: The process is waiting for some event to occur (such as an I/O completion or reception of a signal).
- Ready: The process is waiting to be assigned to a processor.
- Terminated: The process has finished execution.
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