Process Management (week 5)

Question 1

what is a program

Answer 1

a program is a binary program in execution

Question 2

what is a process made up of

Answer 2

a binary program

data on which the program will execute

resources required for execution, including the files, devices which contain or provides the data required
–> some examples are CPU time, input-output devices, files, etc

Question 3

multiple processes can be generated from _________

Answer 3

1 program file

for example you can only have one browser program but you can have multiple processes running in that program (opening multiple windows)

Question 4

true or false
process also contains memory stack space

Answer 4

true

Question 5

how many threads in 1 process are there in the classic process design

Answer 5

one as there is only one execution engine per process

Question 6

how many threads in 1 process are there in the modern computer

Answer 6

multiple threads as there is multiple execution engines per process

Question 7

threads can be thought of as

Answer 7

subprocesses

Question 8

Describe what is a thread

Answer 8

a thread is a single execution engine capable of performing a series of instructions in a computer program

In a multiple threaded process, each thread needs to maintain its own set of data in order to perform its own series of instructions.

Question 9

what is an example of threads

Answer 9

A word processor may have a thread for
–> displaying graphics,

–> another thread for responding to keystrokes from user

–>third for performing spelling and grammar checking in the background

Question 10

where is thread specific data stored

Answer 10

Thread specific data is private to the thread. This data is usually stored in a stack.

Question 11

thread specific data includes:

Answer 11

–> Program counter
–> Status of thread
–> processor registers
–> stack space

Question 12

threads within the same process share ?

Answer 12

–> Program code
–> Data
–> Resources

Question 13

threads are also called

Answer 13

lightweight processes

Question 14

in unix process, OS kernel creates a _____________ to
manage process

Answer 14

process descriptor

Question 15

in unix process, what is process identifier

Answer 15

it is the User handle for the process (descriptor)

Question 16

what does the linux command ps -aux display

Answer 16

list of all the processes running on your system

Question 17

how will the os create a new process in the windows NT model

Answer 17

user program makes a system call to request to the kernel to activate the create process function

all this must happen in supervisor mode and not user mode

Question 18

benefits of multithreaded process

Answer 18

–> more responsive
–> resource sharing (easier for the os to allocate resources to each process and the process will further allocate to the threads)
–> ease of memory and resource allocation
–> utilization of multiprocessor architectures

Question 19

what is a process manager

Answer 19

To manage multiple processes, modern OS
implement the process manager to manage the
processes.

Question 20

what does the process manager implement

Answer 20

–> Calls like fork() in UNIX and CreateProcess() in
windows to create processes.

–> Calls like pthread_create() in Linux and
CreateThread() in Windows to support threading.

–> Calls like close() in Unix and CloseHandle() in
Windows to close processes/threads to release
resources.

Question 21

what are the responsibilities of the process manager

Answer 21

–> Define & implement the essential characteristics of a
process and thread
–> Algorithms to define the behavior
–> Data structures to preserve the state of the execution
–> Define what “things” threads in the process can
reference – the address space (most of the “things”
are memory locations)
–> Manage the resources used by the processes/threads
–> Tools to create/destroy/manipulate processes & threads —-> Tools to schedule the processes on the CPU.
–> Tools to allow threads to synchronize the operation with one another.
–> Mechanisms to handle deadlock.
–> Mechanisms to handle protection.

Question 22

what information does the process descriptor store

Answer 22

–> Process ID
–> Program counter
–> Register values
–> Process state
–> Type & location of resources it holds
–> List of resources it needs
–> Security keys

Question 23

process descriptor is also called

Answer 23

process control block (PCB)

Question 24

what is a context

Answer 24

In a multiple process environment, each
thread of execution is a context

Question 25

what is a context switch

Answer 25

a context switch happens when the CPU switches between two processes/threads

Question 26

when can the context switch occur

Answer 26

A context switch can only occur when the
OS gets control of the CPU through traps
or interrupts (happens when os gets access to CPU by switching to supervisor)

Question 27

what is running state

Answer 27

: Instructions are being executed

Question 28

what is Blocked state

Answer 28

The process is waiting for some event to
occur (eg, I/O completion)

Question 29

what is Ready state

Answer 29

The process is waiting to be assigned to a
processor.

Question 30

what is done state

Answer 30

The process has finished execution

Question 31

true or false

Modern OS implements additional states as
required to support more complex features.

Answer 31

true