Process Managment

Question 1

What is a program?

Answer 1

A set of instructions for performing a task

Question 2

What is a process?

Answer 2

A program in execution

Question 3

What are the 5 process states?

Answer 3

Born, Ready, Waiting, Running, Died

Question 4

What happens when a process is born?

Answer 4

A process is created but has not yet been admitted to the pool of executed processes

Question 5

When is a process transferred to the ready state?

Answer 5

When the OS is ready for the process, or if another process is required.

Question 6

Why does the processor transfer a process between ready and running?

Answer 6

A process is transferred based on a priority its assigned by the processor.

Question 7

When is the waiting stage used?

Answer 7

When waiting for input from an I/O device or when the process has made a request it has to wait for.

Question 8

When does a process die?

Answer 8

When it has been completed or aborted

Question 9

What is a Process Control Block?

Answer 9

the PCB represents a process and is stored in memory or on disk.

Question 10

What data does the Process Control Block Contain?

Answer 10

The process number/ID, the processes registers, the process address space, the process I/O.

Question 11

What term is used to describe switching processes?

Answer 11

Context Switch or a Process Switch

Question 12

How does a context switch take place?

Answer 12

Change Process Scheduling State of process A, save the context of process A (save variables form registers to memory), load context of process B, change Process Scheduling state of process B.

Question 13

What is contained in the process address space?

Answer 13

Stack for temp data, heap for dynamically allocated data, data section for static data, text section for program code.

Question 14

How and why is a Heap used?

Answer 14

Blocks of memory are allocated and removed in an arbitrary order of any required size. It is used to store a large block of memory for a longer period of time, and variables that can change size.

Question 15

What interaction can happen between the Stack and the Heap?

Answer 15

As the stack and the heap grow they grow towards each other in memory, this means that if they aren’t properly controlled they can start to overwrite each other.

Question 16

What is process spawning?

Answer 16

When One process is created at the request of another process. These are parent and child processes.

Question 17

How many commands does Linux have for process spawning?

Answer 17

4

Question 18

What does the fork command do?

Answer 18

Creates a child process with a unique process ID. The child is given a copy of the process address space of the parent.

Question 19

What does the Exec command do?

Answer 19

Runs a executable file that overwrites the process address space with a new program.

Question 20

What does the Wait command do?

Answer 20

Puts the parent process in the waiting state until the child process has completed.

Question 21

Why is interprocess communication used?

Answer 21

Some processes are interested in the same information, this is used when a processes is divided into subtasks.

Question 22

How can interprocess communication be implemented?

Answer 22

Shared Memory or Message Passing.

Question 23

How is shared memory implemented?

Answer 23

Memory Space from one of the Processes is shared between them. The processes make calls to the kernel to share or to read/write data from the shared space. The processes are responsible they don’t write to the same space simultaneously.

Question 24

How is Message Passing Implemented?

Answer 24

Processes communicate by sending messages. Messages are sent and received using a “mailbox” that is not part of the address space of any of the processes. Message passing system must provide send and receive operations.