Process (computing)

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Concepts- Program vs. Process vs. Thread

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Process states

Process (computing) is a fundamental concept in computer science and operating systems that refers to an instance of a computer program that is being executed. A process can be thought of as a program in action, consisting of the program code (also known as the text section), its current activity represented by the program counter, and the contents of the processor's registers. A process also includes the process stack, which contains temporary data such as method parameters, return addresses, and local variables, and a heap, which is a memory area allocated for dynamic memory allocation.

Definition

In computing, a process is an instance of a computer program that is executed sequentially by a Central Processing Unit (CPU). Each process is a running instance that includes the program code and its current activity. Operating systems support process creation for executing user commands and running system programs. Processes can communicate with each other through Inter-process communication (IPC) mechanisms and can synchronize their actions.

Characteristics

A process has several characteristics, including an Identifier (PID), which uniquely identifies each process within the system; a state, which indicates the current status of the process (e.g., running, waiting, stopped); a priority, which influences the process's scheduling; and a context, which includes the process's current values of the program counter, registers, and variables.

Process States

The life cycle of a process in an operating system involves several states:

• New: The process is being created.
• Ready: The process is waiting to be assigned to a processor.
• Running: Instructions are being executed.
• Waiting: The process is waiting for some event to occur (such as an I/O completion or a signal).
• Terminated: The process has finished execution.

Process Control Block (PCB)

Each process is represented in the operating system by a Process Control Block (PCB), which contains important information about the process, such as its PID, state, priority, and associated resources. The PCB is essential for the operating system to manage and schedule processes efficiently.

Scheduling

Process scheduling is a key activity of the operating system, which decides which process runs at any given time. Scheduling algorithms, such as First-Come, First-Served (FCFS), Shortest Job First (SJF), and Round Robin (RR), are used to optimize the use of CPU time and ensure that all processes are executed fairly.

Inter-process Communication (IPC)

Processes often need to communicate with each other to exchange data or synchronize their actions. This is achieved through IPC mechanisms, such as pipes, message queues, semaphores, and shared memory.

Multithreading

In addition to processes, modern operating systems support multithreading, where a process can have multiple threads of execution running concurrently. This allows for more efficient use of resources and faster execution of programs.

Security and Isolation

Processes are isolated from each other by the operating system to prevent unauthorized access to memory and resources. This isolation ensures that a failure in one process does not affect the execution of other processes. Security mechanisms, such as user permissions and access controls, are applied to processes to control their access to system resources.