Process Managmennt

PROCESS MANAGMENNT

Processes • Early computer systems allowed only one program to be executed at a time. This program had complete control of the system and had access to all the system’s resources. • In contrast, current-day computer systems allow multiple programs to be loaded into memory and executed concurrently. • This evolution required firmer control and more compartmentalization of the various programs, and these needs resulted in the notion of a process, which is a program in execution. . A process is the unit of work in a modern timesharing system.

Program vs Process • A process is a program in execution. For example, when we write a program in C or C++ and compile it, the compiler creates binary code. The original code and binary code are both programs. When we actually run the binary code, it becomes a process. • A process is an ‘active’ entity, as opposed to a program, which is considered to be a ‘passive’ entity. A single program can create many processes when run multiple times; for example, when we open a .exe or binary file multiple times, multiple instances begin (multiple processes are created).

What does a process look like in memory? A process is more than the program code, which is sometimes known as the text section.

It also includes the current activity, as represented by the value of the program counter and the contents of the processor’s registers. A process generally also includes the process stack, which contains temporary data (such as function parameters, return addresses, and local variables), and a data section, which contains global variables. A process may also include a heap(mass), which is memory that is dynamically allocated during process run time

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 state : Initially process will be in New state . It means process is under creation or process is being created . Ready state : Once the process is created it will be moved on to ready state . In the ready state there will be multiple number of process . Running state : One of the process will be selected from the ready state and dispatched on to the running state .When the process in the running state it occupied the CPU and executing the instruction of the process and performing CPU time . Waiting State: If the running process required any input output then it will come to wait state . Terminated. The process has finished execution.