Process Manager

Question 1

Process

Answer 1

The unit of work in computer system.

Sequence of states, resulting in action of set of instructions on states as they develop.

Question 2

How does OS manage processes?

Answer 2

OS maintains a data structure called Process Control Block for each process.

Enables the OS to manage different processes effectively, by saving current state in the Process Control Block, switching between them and reloading certain processes later on.

Question 3

Static part :

Answer 3

-Certain amount of space in memory

-A current working directory

-Sources of input and output such as a keyboard, screen and open files

-A connection with another process over a network

-A program (sequence of instructions - inert)

Question 4

Dynamic part:

Answer 4

Instructions that make up program

Thread execution

Thread has access to all of resources assigned to task

Question 5

Operating System Overhead

Answer 5

Happens when process begins running and stop abruptly to wait for input.

OS has to save or restore the whole state of machine at moment the process stopped running.

Saving and restoring, becomes large part of the computer.

Increasing size of operations makes OS more complex.

Question 6

Multi-threading

Answer 6

The OS overhead led to the idea of having number of path of executions through the program at the same time.

Not necessary to save and restore the full state of machine, as using same memory files and device.

Each thread must maintain state info of its own.

Multithreading enables processing of multiple threads at one time, rather than multiple processes.

Multithreading increases performance efficiency and scalability.

Question 7

Type of Threads

Answer 7

User Threads
Kernel Threads

Question 8

User Threads

Answer 8

Threads that application programmers use in their programs.

Saves overhead on the OS each time thread changes to another. THE OS gives control of the CPU to a process.

Question 9

Kernel Threads

Answer 9

Supported within the Kernel of OS.

OS handles all the switching between threads.

Kernel can perform multiple simultaneous tasks.

Question 10

Process, Tasks and Threads

Answer 10

OS needs to keep track of processes. Uses “processor control block” to represent different objects.

A processor consists of a task, where resources are allocated one or more threads, or controls paths through code.

Possible to represent one task and variable number of threads. Needs a static part and dynamic part that can grow or shrink.