Chapter 3

Question 1

Define a process

Answer 1

a program in execution, unit of work in a modern time-sharing system, sometimes known as text section, represents current activity with program counter, contents of processor’s registers, includes process stack, a data section, may include a heap, and performs single thread of execution

Question 2

A system consists of a collection of process and different codes are associated to different thing. what is OS and user associated with?

Answer 2

system code and user code

Question 3

what does the batch system execute

Answer 3

jobs

Question 4

what does a time-sharing system execute

Answer 4

user programs or tasks

Question 5

when does a program become a process

Answer 5

when an executable file is loaded into memory

Question 6

name a couple of states of a process

Answer 6

new, running, waiting, ready, terminated

Question 7

what is PCB

Answer 7

process control block

Question 8

define program counter

Answer 8

address of next instruction to be executed

Question 9

define cpu registers

Answer 9

different type of registers, when an interrupt occurs the status info is saved

Question 10

define cpu-scheduling information

Answer 10

process priority pointers to scheduling queues

Question 11

define memory management information

Answer 11

value of base, limit registers, page tables, etc.

Question 12

define accounting information

Answer 12

amount of CPU information and real-time used, time limits account numbers, etc

Question 13

define I/O status information

Answer 13

list of I/O devices allowed to process, etc.

Question 14

describe single thread in 5 words

Answer 14

one task at a time

Question 15

define multiprogramming objective

Answer 15

some process running at all times, to maximize cpu utilization

Question 16

define time-sharing objective

Answer 16

switch cpu among processes so frequently that users can interact with each program while it is running

Question 17

define process scheduler

Answer 17

selects available process for program execution on the cpu

Question 18

define batch system and process

Answer 18

more processes are submitted that can be executed immediately, then spooled to a mass-storage device, where they are kept for later execution. then long-term scheduler selects processes from this pool and loads into memory for execution. short-term scheduler selects from among processes that are ready to execute and allocates cpu to one of them

Question 19

what is the difference between job and cpu scheduler

Answer 19

frequency of execution

Question 20

define short-term scheduler

Answer 20

cpu scheduler, more frequent, fast, selects from ready state and allocated cpu to one of them

Question 21

define long-term scheduler

Answer 21

job scheduler, less frequent, slow, controls degree of multiprogramming, makes careful selection, selects and loads to memory

Question 22

define medium-term scheduler

Answer 22

sometimes removes process from memory and reduces degree of multiprogramming

Question 23

define swapping

Answer 23

process is swapped out and later in by medium-term scheduler

Question 24

define context-switch

Answer 24

switching cpu to another process requires performing a state save of current process and a state restore of a different process, pure overhead

Question 25

steps of context switch

Answer 25

• kernel saves context of old process in its PCB

- loads saved context of new process scheduled to run

Question 26

what is a pid

Answer 26

process identifier, integer number, unique value for each process in the system and can be used as an index to access various attributes of a process within kernel

Question 27

when a process creates a new process, what are the 2 possibilities for execution that exist

Answer 27

1. parent continues to execute concurrently with its children
2. parent waits until some or all of its children have terminated

Question 28

what are the 2 address-space possibilities for new processes

Answer 28

1. child process is the duplicate of the parent process

2. children program has new program loaded into it

Question 29

what are some reasons why a parent may terminate the execution of one of its children

Answer 29

• child has exceeded usage of allocated resources
• task assigned to child is no longer required
• parent is exiting and child cannot exist while parent is gone

Question 30

define zombie process

Answer 30

a process that has terminated but whose parent has not yet called wait(), this is a brief moment of time

Question 31

define orphans

Answer 31

parent did not invoke wait() and instead terminated

Question 32

define independent process

Answer 32

cannot affect or be affected by the other processes executing in the system

Question 33

define dependent process

Answer 33

CAN affect or be affected by the other processes executing in the system

Question 34

define information sharing

Answer 34

concurrent access to “shared files”

Question 35

define computation speedup

Answer 35

multiple processing core so subtasks can run in parallel

Question 36

define modularity

Answer 36

system function separately or threads

Question 37

define convenience

Answer 37

compiling in parallel

Question 38

define interprocess communication

Answer 38

IPC, required by cooperating process to exchange data and information

Question 39

what are 2 fundamental modes of interprocess communication

Answer 39

1. message passing

2. shared memory

Question 40

define shared memory

Answer 40

shared memory regions resides in the address space of the process creating the shared-memory segment, 2+ processes agree to remove the restriction of one process not being able to access another’s info

Question 41

what are the two types of buffers

Answer 41

1. unbounded buffer : no practical limit

2. bounded buffer : fixed buffer size

Question 42

define message-passing systems

Answer 42

• allows processes to communicate and to synchronize their actions without sharing the same address space
• useful where processing may reside on different computers connected by a network

Question 43

what are some communicating link methods

Answer 43

• direct/indirect communication
• synchronous/asynchronous communication
• automatic/explicit buffering

Question 44

what is the naming purpose

Answer 44

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

Question 45

what are some communication link properties

Answer 45

• link is automatic between every pair
• link with exactly 2 processes
• one link between each pair of processes

Question 46

what are some indirect communication properties

Answer 46

• link between a pair of processes only if both members of the pair have a shared mailbox
• link with 2+ processes
• between each pair of communicating processes, a number of different links may exist, with each link corresponding to one mailbox

Question 47

define blocking send

Answer 47

sending process is blocked until message is received by the receiving process or by the mailbox

Question 48

define nonblocking send

Answer 48

sending process sends the message and resumes operation

Question 49

define blocking receive

Answer 49

receiver blocks until a message is available

Question 50

define nonblocking receive

Answer 50

receiver retrieves either a valid message or a null

Question 51

what are three way to implement buffering

Answer 51

1. zero capacity : queue length 0
2. bounded capacity: finite queue length
3. unbounded capacity : “infinite” queue length