Lecture 1

Question 1

ps -A

Answer 1

On a Linux system, displays every active process

Question 2

Parent of all processes on the system

Answer 2

init
systemd
launchd

Question 3

How is PCB implemented in linux?

Answer 3

As the data structure task_struct

Question 4

How is PCB implemented in Darwin?

Answer 4

As a data structure task.

Question 5

What is the most complicated data structure in the operating system?

Answer 5

The process block

Question 6

Job queue

Answer 6

Set of all processes in the system

Question 7

Ready queue

Answer 7

set of all processes in main memory, ready and waiting to execute.

Question 8

Device queues

Answer 8

set of processes waiting for a particular I/O device

Question 9

Scheduling

Answer 9

used to determine which process is next to get access to CPU.

Question 10

How are queues implemented?

Answer 10

As a doubly linked list of PCBs

Question 11

What are the reasons for cooperating processes? (IPC)

Answer 11

1. Computation speedup (parallelization)
2. Information sharing
3. Modularity

Question 12

What are the two models of IPC?

Answer 12

1. Shared memory

2. Message passing

Question 13

Example of shared memory in Unix

Answer 13

POSIX shared memory Unix

Question 14

How does a process terminate another process?

Answer 14

Via a System call
TerminateProcess() in windows
abort() in Unix/Linux

Question 15

How does a parent know which child to terminate?

Answer 15

The child id is passed to the parent when the child is created.

Question 16

Does the OS allow a child to continue if its parent terminates?

Answer 16

NO

Question 17

The process is a Zombie when?

Answer 17

No parent waiting, hasn’t invoked wait() yet.

Question 18

A process is an orphan when?

Answer 18

Parent terminates without invoking wait().

Question 19

ps -ef

Answer 19

In Linux will display kernal threads

Question 20

Parent of all other kernel threads?

Answer 20

kthreadd (pid = 2)

Question 21

Examples of message passing

Answer 21

 Windows advanced local procedure (ALPC) facility
 Pipes (named or unnamed)
 Client-server communication
     - Sockets
     - Remote Procedure Calls (RPCs)

Question 22

What are the reasons a parent might terminate a child process?

Answer 22

 Child has exceeded allocated resources
 Task assigned to child is no longer required
 The parent is exiting and the operating systems does not allow a child to continue if its
parent terminates

Question 23

On UNIX systems what happens to orphaned processes?

Answer 23

They are inherited by process with pid 1 which then proceeds to kill them.