Ch 3

Question 1

Process Block

Answer 1

Text section: code

Data: global variables

Heap: dynamically allocated variables

Stack: temporary data (function parameters, return addresses, local variables)

Question 2

Process States

Answer 2

New. The process is being created.

Running. Instructions are being executed.

Waiting. The process is waiting for some event to occur (such as an I/O completion or reception of a signal).

Ready. The process is waiting to be assigned to a processor.

Terminated. The process has finished execution.

Question 3

PCB

Answer 3

contains information associated with each process: process state, PC, CPU registers, scheduling information, accounting information, I/O status information

Question 4

Thread

Answer 4

A thread allows a process to perform one task

Question 5

job queue

Answer 5

All processes in the system

Question 6

ready queue

Answer 6

process in main memory ready and waiting for execution

Question 7

device queue

Answer 7

processes waiting for a particular I/O device

Question 8

long term vs short term job scheduler

Answer 8

long term scheduler chooses jobs and allocates them into main memrory

short temr scheduler chooses processes ready to execute and allocates them to a CPU (chooses teh degree of multi programing)

Question 9

medium term scheduling

Answer 9

swapps process form memory and stores into disk to reduce degree of multiprogramming

it saves the state int PCB

Question 10

Context Switch

Answer 10

context represented in the PCB to restore the state of the process when loaded back into memory after swapping

has time overhead since the CPU does no useful work while switching

Time of a context switch is dependent on hardware

Question 11

pid

Answer 11

process identifier assigned by either a parent process or the Operating System

Question 12

cascading termination

Answer 12

A phenomenon where the children are also terminated when the parent is terminated (actually when the child is terminated before the parent)

Question 13

zombie

Answer 13

A process that has terminated, but whose parent has not yet called wait()

Once the parent calls wait(), the process identifier of the zombie process and its entry in the process table are released.

Question 14

orphan

Answer 14

when the process’ parent does not call wait and is instead terminated.

Question 15

IPC

Answer 15

interprocess communication allows for a cooperative process to exchange information

Either message-passing or memory-sharing

Question 16

shared memory (IPC)

Answer 16

In the shared-memory model, a region of memory that is shared by cooperating processes is established. Processes can then exchange information by reading and writing data to the shared region.

Question 17

message passing (IPC)

Answer 17

communication takes place by means of messages exchanged between the cooperating processes

Question 18

socket

Answer 18

an endpoint for communication

defined by an IP address along with a port number

Concatenation of IP address and port

http - port 80

ftp - 21

Question 19

shared memory systems

Answer 19

Producer

Consumer

bounded buffer

unbounded buffer

Question 20

message passing systems

Answer 20

direct communication - each process that wants to communicate must explicitly name the recipient or sender of the communication.

(symetric addressing)

send(P, message)—Send a message to process P.

receive(Q, message)—Receive a message from process Q.

(asymetric addressing)

send(P, message)—Send a message to process P.

receive(id, message)—Receive a message from any process. The variable id is set to the name of the process with which communication has taken place.

Indirect Communication - the messages are sent to and received from mailboxes, or ports.

send(A, message)—Send a message to mailbox A.

receive(A, message)—Receive a message from mailbox A.

Question 21

Message Syncronization

Answer 21

Blocking (synchronous) - The sending process is blocked until the message is received by the receiving process or by the mailbox. The receiver blocks until a message is available.

Nonblocking (asynchronous) - The sending process sends the message and resumes operation. The receiver retrieves either a valid message or a null.

FROM STUDY GUIDE

Blocking is considered synchronous

▪ Blocking send has the sender block until the message is received

▪ Blocking receive has the receiver block until a message is available ◦ Non-blocking is considered asynchronous

▪ Non-blocking send has the sender send the message and continue

▪ Non-blocking receive has the receiver receive a valid message or null

Question 22

ordinary pipes

Answer 22

One of the first IPC mechanisms in UNIX. Acts as a conduit allowing two processes to communicate.

One write-only end and one read-only end.

Uniderectional

Question 23

named pipes

Answer 23

are bidirectional

Question 24

stub

Answer 24

provided to client by an RPC, which hides details that allows communications to take place, it locates port on the servers, marshals the parameters, and transmits/recieves messages to the server

Question 25

coopertive process

Answer 25

when processes are dependant of one another

Question 26

Types of processes

Answer 26

I/O Bound: spends more time doing I/O than computations, many short CPU bursts ◦ CPU Bound: spends more time doing computations, few very long CPU bursts

Question 27

PID FACTS

Answer 27

PID allows for process management ◦ Parents and children can share all/some/none resources ◦ Parents can execute concurrently with children or wait until children terminate

◦ fork() system call creates new process

▪ exec() system call used after a fork to replace the processes’ memory space with a new program

▪ review code examples

Question 28

RPC vs RMI

Answer 28

RPC

invokes FUNCTIONS through proxy. allows the remote procedure call among different languages.

RMI

invokes METHODS through proxy. is designed specifically for Java, thus it is easer to use.