Operating Systems Final Topics Part 2

Front 1

What is a process state?

Back 1

When a process executes, it changes state

Front 2

List the process states

Back 2

New - process being created

Running - instructions are being executed

Waiting - waiting for an even to occur

ready- the process is waiting to be assigned to a processor

Terminated - The process has finished execution

Front 3

How many processes can be running at a time?

Back 3

One can be running on any processor at any instant. However many processes may be ready and waiting.

Front 4

What is the other name for Process Control Block (PCB)?

Back 4

Task control Block

Front 5

What are the process control block?

Back 5

It is a process associated with process states, program counter, cpu registers, cpu-scheduling information, memory management, accounting information, and I/O status.

Front 6

What is a program counter?

Back 6

The counter indicates the address of the next instruction to be executed for this process.

Front 7

What is a CPU register?

Back 7

The registers very in number and type, depending on the architecture.

Front 8

What does the CPU register include?

Back 8

Accumlators

Index registers

stack pointers

general purpose registers

an condition code info

Front 9

List the CPU-scheduling information

Back 9

Process priority

pointers to scheduling queues

Any other parameters

Front 10

What is memory management information?

Back 10

May include such items as the value of the base and limit registers and the pages tables or the segment tables.

Front 11

List the accounting information

Back 11

Includes

amount of CPU

Real time used

time limits

account numbers

job or process numbers

Front 12

List the I/O status info

Back 12

Includes

I/O devices

Allocated to the process

a list of open files

Front 13

What is interprocess communication?

Back 13

Processes within a system may be independent or cooperating.

Cooperating process can affect or be affected by other processes, including shared data

Front 14

What are the reasons of cooperating process?

Back 14

Information sharing

Computation speedup

Modularity

Convenience

Front 15

What does the cooperating process need?

Back 15

Interprocess communication (IPC)

Front 16

What are the two models of IPC?

Back 16

Shared memory

message-passing

Front 17

What is shared memory?

Back 17

Requires communicating processes to establish a region which resides in the address space of the process creating shared-memory segment.

read and write in the same shared areas.

Front 18

What are the two types of buffers?

Back 18

Unbounded Buffer - places no practical limit on the size of the buffer.

Bounded Buffer- fixed buffer size.

Front 19

What is message-passing?

Back 19

Provides a mechanism to allow processes to communicate and to synchronize their actions without sharing the same address place.

Communication link must exist.

Front 20

What are the different communication links?

Back 20

Direct or indirect communication

Synchronous or asynchronous communication

Automatic or explicit buffering.

Front 21

What is the difference between threads and processes?

Back 21

Process creation are heavy-weight.

Threads are light-weight.

Threads are responsive, resource sharing, economical and scalability.

Front 22

What are the user thread to kernal thread mapping?

Back 22

many-to-one model

One-to-one model

Many-to-many model

Two-level model

Front 23

What is many-to-one model?

Back 23

Single kernal thread

Efficient but process may block if thread makes a blocking system call

Front 24

What is one-to-one model?

Back 24

Each thread maps to kernal

Allows multiple thread to kernal

Front 25

What is many-to-many model?

Back 25

Allow many threads to be mapped to many kernals.

Front 26

What is two-level model?

Back 26

Bound to kernal thread

Front 27

What is PThread library?

Back 27

It's the posix library for creating threads.

Front 28

Shared memory and message passing are two models of interprocess communication. Briefly describe each.

Back 28

The shared memory modes consists of processes sharing a region of their respective memory spaces, so that when one process writes to this region, the other processes sharing it can see the newly written data. The message passing model consists of processes sending messages to other processes using the kernal as an intermediary.

Front 29

Why is exec() generally called after fork() when there is no equilvalent functions called after CreateProcess()?

Back 29

CreateProcess() takes as an argument that name of an executable file to execute, whereas fork() simply creates a copy of the current process. IN order to create a child process that will execute a different executable file than the parent's, a processes must call exec() after fork().

Front 30

Give two advantages of creating multiple threads instead of multiple processes in a parallel program.

Back 30

Creating threads involves less overhead for the kernel than creating processes. Threds share a global memory space, facililtating communication between them.

Front 31

Which of the following components of program state are shared across threads in a multithreaded process?

a. Register values

b. heap memory

c. Global variables

d. Stack memory

Back 31

b and c are shared across threads.

Front 32

What are the two models of interprocess communication? What are the strengths and weaknesses of the two approaches?

Back 32

The two models are shared memory and message-passing. Shared memory allows direct exchanges of information, but requires processes to manage access to that information to prevent conflicts from occurring. Message-passing prevents conflicts, but also incurs additiona overhead.

Front 33

Look at question 3, wednesday night quiz 2.

Back 33

child: pid = 0, pid1 = <child pid>

parent: pid = <child pid>, pid1 = <parent pid>