Intro to OS Exam 1 1---Explain what each of the following commands do, as well a

Question

Intro to OS Exam 1

1---Explain what each of the following commands do, as well as which operating system uses them (1.5 pts each):

ls

Cd

Grep

Dir

Type

Cat

Ps

Mv

Robocopy

Sed

Sudo

chmod

2---What is an environment variable? What does the PATH environment variable contain? What is PATH used for? (4 pts)

3---What are the 4 major jobs of a modern operating system? (4 pts)

4---In memory management, what is the role of a 'dirty bit', and why do we keep track of it? (3 pts)

5---What is meant by the term 'user mode', and what is meant by the term 'kernel mode'? (4 pts)

6---What is a working set? (2 pts)

7---What is the first line of every bash script? (2 pts)

8---What is the permission string (RWXRWXRWX format) of the number 311 (2 pts)

9---What is the base directory of a file system called on windows (1pt), and on linux (1 pt).

10---What does the term 'super user' mean in terms of operating systems (2 pts).

11) EXTRA CREDIT: (3 pts)
You have been hired to test the capacity of Al Harrington's ShatterProof Snibbets to work after they are dropped from large heights. You have been given 2 Snibbets, and access to a 100 story building. You need to determine the maximum floor the Snibbets can be dropped from without shattering. You only have time to test 20 floors. How can you do this? Can you do it in less than 15 test drops?

Explanation / Answer

NOTE: Didnt have much time, therefore answered only 7, please repost the question with only the remaining parts.

1)

ls - ls is a Linux shell command that lists directory contents of files and directories.

Cd - used to switch between directories

grep - grep is a command-line utility for searching plain-text data sets for lines that match a regular expression

Dir - The dir command allows you to see the available files and directories in the current directory.

chmod - used for file permissions

sudo - allows users to run programs with the security privileges of another user, by default the superuser.

3) The 4 major jobs are:

i) Managing programs

ii) Managing Memory

iii) Handling input and output

iv) User Interface

4) The dirty bit is set when the processor writes to (modifies) this memory. Dirty bits are used by the CPU cache and in the page replacement algorithms of an operating system. Dirty bits can also be used in Incremental computing by marking segments of data that need to be processed or have yet to be processed.

5) In Kernel mode, the executing code has complete and unrestricted access to the underlying hardware. Whereas In User mode, the executing code has no ability to directly access hardware or reference memory.

6) memory required by a process in a particular time interval

7) #!/bin/bash

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