1
Process
Description
&
Control
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Operating System Process Control Block and Process States, Slides of Operating Systems
The concepts and elements of an operating system's process control block (pcb) and the different process states in an operating system. It covers the process creation, termination, and the two-state and five-state process models. The document also explains the reasons for process suspension and the operating system control structures, such as memory tables, i/o tables, file tables, and process tables.
Typology: Slides
2011/2012
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Process
Description
Control
Requirements of an Operating System
Interleave the execution of multiple
processes to maximize processor utilization
while providing reasonable response time
Allocate resources to processes
Support interprocess communication and
user creation of processes
Manage Execution of Applications
Resources made available to multiple
applications
Processor is switched among multiptle
application
The processor and I/O devices can be used
efficiently
Process
A program in execution
An instance of a program running on a computer
The entity that can be assigned to and executed on
a processor
A unit of activity characterized by the execution of a
sequence of instructions, a current state, and an associated set of system instructions
Process Control Block
Memory pointers
Includes pointer to data and memory address
Context data
These are data that are present in registers
I/O status information
Include I/O request , I/O devices and list of files used by the process
Accounting information
Includes amount of processor time, clock time used time limits and so on.
Process Control Block
Contains the process elements
Created and manage by the operating system
Allows support for multiple processes
Trace of Process
Sequence of instruction that execute for a
process
Dispatcher switches the processor from one
process to another
Example Execution
Two-State Process Model
Process may be in one of two states
Running
Not-running
Process Creation
Process Termination
Processes
Not-running
ready to execute
Blocked
waiting for I/O
Dispatcher cannot just select the process that
has been in the queue the longest because it
may be blocked
A Five-State Model