Lecture 3

Question 1

A process is…

Answer 1

…a program in execution

Question 2

A process has at least the following:

Answer 2

• Program counter
• Stack
• Data section

Question 3

Difference between program and process

Answer 3

Program is the actual file on the disk, process is the job

Question 4

When you execute a file, the OS…

Answer 4

…invokes a process (allocates whatever the program requires to run)

Question 5

Another word for a process is a…

Answer 5

…job

Question 6

The stack stores the ____ and grows from ____ to ____

Answer 6

Local variables, max to 0

Question 7

The heap stores the ____ and grows from ____ to ____

Answer 7

Dynamically allocated memory, 0 to max

Question 8

Data stores ____ and is below the ____

Answer 8

Global variables, heap

Question 9

Text stores ____ and is below the ____

Answer 9

Program code, data

Question 10

As a process executes, it changes its…

Answer 10

…state

Question 11

Process States:

Answer 11

• New (just created)
• Running (Instructions being executed)
• Waiting (Waiting for an event to occur)
• Ready (Waiting for the CPU)
• Terminated (Process has finished execution)

Question 12

OS maintains info about process in…

Answer 12

…PCB (Process Control Block)

Question 13

PCB contains what info?

Answer 13

• Process State
• Program Counter
• CPU registers
• CPU scheduling info
• Memory-management info
• Accounting info
• I/O status

Question 14

PCB used to…

Answer 14

…switch CPU from one process to another

Question 15

PCB in Linux is represented by…

Answer 15

…the C structure task_struct (in a doubly linked list)

Question 16

Processes are maintained in…

Answer 16

…queues

Question 17

Ready Queue

Answer 17

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

Question 18

Device Queues

Answer 18

Set of processes waiting for an I/O device

Question 19

Two types of processes in queues

Answer 19

CPU bound and I/O bound

Question 20

When CPU switches from process to process, the kernel…

Answer 20

…saves the state of the first process in first PCB, then loads the state of the second process from second PCB into registers

Question 21

Context-switch time is…

Answer 21

…pure overhead (no useful work is done)

Question 22

Typically ____ for switching

Answer 22

A few milliseconds

Question 23

Processes may create other processes, forming a…

Answer 23

…tree

Question 24

Process creates a child process using…

Answer 24

…fork system call

Question 25

Child is a ____ of the parent

Answer 25

copy

Question 26

Typically, child loads another program into its address space using…

Answer 26

…exec system call

Question 27

Parent waits for…

Answer 27

…its children to terminate