Processes

OPERATING SYSTEMS
PROCESSES

• Process Definition
• Scheduling Processes
• What Do Processes Do?
• Inter-process Communication

OPERATING SYSTEM Processes

Process

A process is :

• An instance of a program in execution

• An asynchronous activity

• The “animated spirit” of a procedure

• The “locus of control” of a procedure in execution

• The “dispatch able” unit

• An unit of work individually schedulable by an operating system.

Formally, we can define a process is an executing program, including the current values of the program counter, registers, and variables. The subtle difference between a process and a program is that the program is a group of instructions whereas the process is the activity.

A program is passive; a process is active.

Process Management Functions

The process management functions include:

• Process creation
• Termination of the process
• Controlling the progress of the process
• Process Scheduling
• Dispatching
• Interrupt handling / Exceptional handling
• Switching between the processes
• Process synchronization
• Inter process communication support
• Management of Process Control Blocks

Process States

• Let us start with these states:
• The Running state
• The process that is executing on the CPU is in the Running state
• The Blocked state
• A process that is waiting for something (e.g. I/O) to complete is in the Blocked state
• The Ready state
• A process that is ready to be executed, but not currently assigned to a CPU, is in the Ready state
• Only one process can be running on any processor at any instant.
• Many processes may be ready and waiting.