Process Concept

Program - passive entry in storage, stored as an executable

Process - a program in execution (baso a program in memory); this must happen is a sequential fashion

Multiple Process can com from 1 Program

Process are made of multiple parts:

• The code, also known as the text section

• The current activity, including the program counter, and process registers

• Stack containing the temporary data (such as functions, local variables, return addresses)

• Data Section containing global variables

• Heap containing memory allocated at run time

Stack and Heap

Process State

As a process executes its state may change:

• New - The process is being created

• Running - Instructions are being executed

• Waiting - Waiting for an event to occur

• Ready - Waiting to be assigned to a processor

• Terminated - Process has finished execution

Process Control Block (PCB)

also known as: Task control block

This is all information associated with each Process

• Process State - is it running waiting...

• Program Counter - Location of next instruction (maybe multiple when using threads)

• CPU Registers - Contents of all the registers associated with the process

• CPU Scheduling Information - Priorities, scheduling pointers

• Memory-management info - memory allocated to the process

• Accounting info - CPU used for the process, clock time since start, time limits

• I/O status info - input output devices allocated to the process, list of open files

Threads

The idea of having multiple program counters per a process,

so multiple locations can execute at the same time