Processes in Operating System
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A process contains the program code, stack, data section, and heap. It is represented in the operating system by a process control block that stores information like the process state, number, program counter, registers, and open files. The operating system uses a scheduler to select processes from memory and choose among ready processes, switching between them through context switching that saves the current process control block and loads the next one.
Processes in Operating System
- 1. Topic: Processes Page 1 out of 7
- 2. Process • Program that is in execution. • More than the program code • Has several parts • Text Section- Contains the code of the program. • Stack- Contains Temporary data(Function parameters, local var, Return address). • Data Section- Contains Global var • Heap- Contains dynamic memory allocated during process run time. Page 2 out of 7
- 3. Process State • New- The process is being created. • Ready- All the resources are available, process is waiting to be assigned to a processor • Running- The CPU is working on this process's instructions. • Waiting- The process is waiting for some event to occur (such as an I/O completion or reception of a signal). • Terminated- The process has finished execution. Page 3 out of 7
- 4. Process or Task Control Block Process is represented in the operating system by a process control block. Contains many information of a specific process including these: • Process State - Ready, Running, waiting, etc. • Process Number – Process number and parent process ID. • Program counter - Indicates the address of the next instruction to be executed for this process. • Registers - This state information must be saved when an interrupt occurs, to allow the process to be continued correctly in further process. • List of open files - It saves device allocated, open file tables, etc. Page 4 out of 7
- 5. Process Scheduler & Context Switching Operating system uses a program scheduler to schedules the processes of computer system • LTS - Selects process from job pool and loads them into memory. • STC - Selects among the processes that are ready to execute. Context Switching: Saves the current PCB and switch into next PCB. This task is known as a context switch. Happens by interrupt or some higher priority task. Page 5 out of 7
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