The concept of process
A process is the basis of the operating system structure; it is a program that is being executed; an instance of the program that is running in the computer; An entity that can be assigned to and executed by a processor; a unit of activity described by a single sequence of executions, a current state, and a set of associated system resources.
1. A process is an entity
Each process has its own address space, which generally includes text region, data region and stack ( stack region).
The text area stores the code executed by the processor; the data area stores variables and dynamically allocated memory used during process execution; the stack area stores instructions and local variables for active procedure calls.
2. A process is an "executing program"
A program is an inanimate entity. Only when the processor gives life to the program can it become an active entity. We call it for the process.
Characteristics of process
Dynamicity: The essence of a process is an execution process of a program in a multi-programming system. The process is dynamically generated and dies dynamically.
Concurrency: Any process can execute concurrently with other processes.
Independence: A process is a basic unit that can run independently, and it is also an independent unit for resource allocation and scheduling by the system.
Asynchronicity: Due to the mutual constraints between processes, the process has intermittent execution, that is, the processes advance at independent and unpredictable speeds.
Structural features: The process consists of three parts: program, data and process control block.
Multiple different processes can contain the same program: a program constitutes different processes in different data sets and can obtain different results; but during execution, the program cannot change.
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