Operating Sys. Quiz 2

Question 1

Difference between “normal” user and “super-user/root”

Answer 1

• “normal” users with a limited set of privileges on the system
• “root” user is the system admin

Question 2

What is the shell?

Answer 2

The shell is essentially a program that allows you to launch other programs

Question 3

What symbol is used for normal users and what symbol is used for root users

Answer 3

$ or % for normals users
# for root users

Question 4

What do command-line programs receive their inputs and outputs from

Answer 4

stdin for inputs
stdout to write their output

Question 5

How can you redirect stdin and stdout

Answer 5

with the < (input) and > (output) redirection operators

Question 6

what does wc -l my file > output.txt do?

Answer 6

sends the output of the wc command to a file called output.txt

Question 7

What do we call “folders” in Finder and similar graphical file navigation tools?

Answer 7

Directories

Question 8

How can every file or directory in the filesystem can be located?

Answer 8

Using its full path name

Question 9

What does pwd, ls and cd do?

Answer 9

• pwd stands for “print working directory”
• ls stands for list the files. Use ls -l to get a “long” detailed listing
• cd stands for “change directory”.

Question 10

What is a shell wildcard?

Answer 10

A wildcard is a symbol that represents a group pf characters in a filename.
The bash offers two wildcards: “*” and “?”

Question 11

What is the difference between the :*” wildcard and the “?” wildcard.

Answer 11

“*” wildcard is a stand-in for zero or more consecutive characters
“?” wildcard is a stand-in for a single character

Question 12

What does echo * do? What about echo../???

Answer 12

• list all the files ( and directories) in the current directory
  -lists all the 3 letter files in the parent directory

Question 13

How do you find the search path

Answer 13

Type “echo path” to display the places the shell searches when you type a command

Question 14

What are pipes?

Answer 14

”|”, pipes allow you to redirect the output of one program and make it the input of another

Question 15

What does ls -l *.txt | wc -l do?

Answer 15

this lists all .txt file one line at a time. wc then counts the number of input lines

Question 16

What does ls -l | awk ‘{print $5}’ do?

Answer 16

prints the size of the files in the directory because that appears in column #5 of the output ls -l

Question 17

what is awk -F ‘ ‘ ‘{print $n}’

Answer 17

Where n is the column of interest. And, optionally, the -F is the firstly separator

Question 18

what does this do:
cat etc/passwd | awk -F’:’{print $5}’ |sort

Answer 18

The cat command dumps the output of the file. The pipe redirects that output to the input of the awk filter which extracts the 5th column. The output of awk is redirected to the input of the sort filter which sorts it

Question 19

What are the file permission groups? In what order are the permissions? Each group starts at every __ letters?

Answer 19

• user, group, other permissions
• 3

Question 20

How do you change the permissions of a file? How would you take away or give a permission?

Answer 20

• chmod myProg o+w
• would give others write permission on the file myProg

Question 21

What is an operating system?

Answer 21

A program that acts as an intermediary between software applications and the hardware of a computer

Question 22

What is the CPU Instruction Cycle?

Answer 22

fetch, decode, execute

Question 23

What is a data wire?

Answer 23

• a data wire is an electric wire used to pass inofrmation between two or more devices one bit at a time
• a wire may hold voltage ( a binary 1) or may have no voltage ( a binary 0)

Question 24

What is a databus?

Answer 24

• When multiple data wires connect a set of components is called a databus
• A bus can simultaneously transfer as many bits of data as there are wires
• the number of wires is called the bus width

Question 25

What is a conceptual abstraction? Logical abstraction?

Answer 25

C.A - Hides complexities of a real system not important in a particular context
L.A - provides a framework for discussing the logical organization of data or things

Question 26

What is the grep command? the tail command? What does this do:grep -i “UNix” geekfile.txt? this tail -n 3 state.txt

Answer 26

• grep is a command used for searching and matching text patterns in files contained in the regular expressions
• primarily used to output the end of a (text) file or to limit the output of a Linux command.
• The -i option enables to search for a string case insensitively in the given file. It matches the words like “UNIX”, “Unix”, “unix”.
• Prints the last ‘num’ lines instead of last 10 lines. num is mandatory to be specified in command

Question 27

How would you estimate the number of files in the iTunes.app directory

Answer 27

ls -l /Applications/iTunes.app | wc -l

Question 28

How to list all commands in the history that made use of the grep command or filter

Answer 28

history | grep -e ‘grep’

The history command displays the history of commands typed at the command prompt

Question 29

Describe the role of a modern operating system. (your answer should include hardware abstraction and resource allocation and management). Provide examples.

Answer 29

A modern operating system’s functions include resource allocation and management, which involves effectively allocating and managing system resources, and hardware abstraction, which creates a layer of abstraction between software and hardware. Linux, macOS, and Windows are a few examples.

Question 30

What are the four main areas of concern for operating systems? Describe each and the O/Ses role in the management of each.

Answer 30

• Process management (controlling applications that are currently running)
• memory management (controlling system memory)
• file system management (arranging and retrieving data from storage)
• device management (managing hardware devices) are the four primary areas of interest for operating systems.
• Task scheduling, memory management, file system organization, and device driver handling are all responsibilities of the operating system.

Question 31

What is a system bus? Your answer should include a discussion of the data bus and the address bus.

Answer 31

The communication channel that links the CPU, memory, and additional peripheral devices is called a system bus. It is made up of an address bus for memory location specification and a data bus for data transfer.

Question 32

Describe the basic components of a computer system and discuss how they are interconnected by the system bus.

Answer 32

The CPU, memory, storage devices, and input/output devices are the fundamental parts of a computer system. These parts are connected to one another via the system bus, which enables communication between them.

Question 33

What is meant by a memory-mapped I/O device?

Answer 33

a piece of hardware thatthe CPU can interact with through memory read and write operations. Its control
registers are mapped to the system’s memory address space.

Question 34

What is a dual-mode operating system? Your answer should include CPU modes and
trapping.

Answer 34

User mode and kernel mode are the two modes of an operating system that is
dual-modal. While kernel mode permits full access for privileged operations, user mode limits access to crucial system resources. Switching between modes is done with a trap.

Question 35

Which is heavier: 10E5 nanogram or .01 milligrams? Explain.

Answer 35

10e5 nanograms is heavier than .01 milligrams 10e5 nanograms = .1 milligrams .1 milligrams > .01 milligrams

Question 36

Which is longer: 789 Megaweeks or 123 Teraseconds?

Answer 36

Because 1 Megaweek is equal to 1 million weeks and 1 Terasecond is equal to 1
trillion seconds, 789 Megaweeks is longer than 123 Teraseconds.

Question 37

Briefly, describe the operation and function of each component of the CPU (CU, MMU,
ALU).

Answer 37

The Control Unit (CU) is in charge of organizing and managing instructions;
the Memory Management Unit (MMU) handles memory-related tasks;
the Arithmetic Logic Unit (ALU) handles logical and mathematical calculations.