Lecture 2: Process / Shell (Part 1)

Question 1

Process Information includes 3 things:

Answer 1

1) Process Stack
2) Data Section
3) Heap

Question 2

Define: Process Stack of Process Info

Answer 2

Includes temporary data:

• function parameters
• local variables
• return address

Question 3

Define: Data Section of Process Info

Answer 3

Includes global variables

Question 4

Define: Heap of Process Info

Answer 4

Memory that is dynamically allocated during run-time

Question 5

Program code of a process is known as:

Answer 5

text section

Question 6

State the 4 process states:

Answer 6

1) New
2) Running
3) Waiting
4) Terminated

Question 7

How is a process represented in the Operating System (OS)?

Answer 7

As a Process Control Block.

Question 8

What is included in a Process Control Block?

Answer 8

Info related to program execution and context info such as:

• PID
• Process State
• Program counter
• CPU Registers
• CPU_Scheduling info
• Memory-Management info
• I/O Status

Question 9

List the 7 broad categories of Operating System services:

Answer 9

1) User Interface
2) Program Executions
3) I/O Operations
4) File Manipulations
5) Resource Allocation
6) Accounting
7) Protection and Security

Question 10

Define: Shell

Answer 10

An interface between user and OS to access OS services. Is a Command Interpreter (a program that accepts commands from the user and interprets the commands)

Question 11

When using the Shell, the execution of a command is done by ________. What does the Shell make use of when carrying out commands?

Answer 11

A separate process (child process) from the shell process. Makes use of System Calls.

Question 12

Does the shell wait for command processes to finish before the user can use it again or can you always use the shell process?

Answer 12

You have to wait (unless you initiate command with the AND sign which runs the command in the background)

Question 13

When a fork system call is made, what does the child process inherit from the parent?

Answer 13

The parent’s state: Same program instructions, variables have the same values, same position in the code. (Parent and child have separate copies of that state).

Question 14

What does fork() return when called?

Answer 14

PID to parent; 0 to child if successful. Else, -1 if failure to fork.

Question 15

If a failure occurs, what will be the main reason behind the failure?

Answer 15

Failure occurs when the limit of processes that can be created is reached.

Question 16

How many returns occur during a fork() system call?

Answer 16

Twice: one to parent, one to child

Question 17

What does the wait() function do?

Answer 17

Used to terminate the parent process when the child terminates

Question 18

During execution, output interleaving is: (Nondeterministic or deterministic?)

Answer 18

Nondeterministic

Question 19

Define: Nondeterministic

Answer 19

Cannot determine output by looking at code

Question 20

Regarding a fork system call, what is the cause behind a failed fork (ie. when fork() returns -1 to parent and sets errno)?

Answer 20

When the limit of processes that can be created is reached

Question 21

Every process has what kind of table associated with it?

Answer 21

A Process File Descriptor Table

Question 22

What does an entry in a process’s Process File Descriptor Table represent?

Answer 22

Each entry represents something that can be read from or written to. Such as:

• file
• screen
• pipe

Question 23

of Processes as a result of n forks is given by:

Answer 23

2^n - 1