6 - Operating Systems

Question 1

What is a driver?

Answer 1

Piece of code the OS needs to communicate with a peripheral device.

Question 2

Functions of the OS ?

Answer 2

Interpret and carry out commands issued by:

• the users of the computer
• the applications programs running on the comp

Question 3

What’s the purpose of OS?

Answer 3

– Control and operate hardware in an efficient way

– Allow the user powerful access to the facilities of the machine

Question 4

Give 2 examples of the OS in action when using a command in the console ?

Answer 4

• ‘javac MyProgram.java’ → the java program needs to be in the memory → javac is loaded into the main memory from the disk by the OS
• ‘ls’ → needs information on the files in the current directory → OS makes requests to the appropriate system code

Question 5

What must an OS do to accept a command from a user?

Hard

Answer 5

– accept the input keystrokes from the keyboard (→ character codes stored somewhere → process it → pass back info → delay between typing and it returning on screen)

– interpret these keystrokes as a command; if it doesn’t understand → give back appropriate error message

– determine the location of the file containing the
code for this command

– read the appropriate blocks of memory from
(secondary storage) device into memory

– transfer control to the program being executed.

Question 6

How often is the device asking the OS for commands ?

Answer 6

Constantly.

Question 7

Other than reading commands and reaching out to the memory, what else does the OS have to do to maintain its integrity ?

Answer 7

Has to provide protective bubble around every program and decide whether some accesses are safe or not.

Safety mechanisms to protect against malicious programs that want to corrupt memory or data files.

Question 8

What are the reasons for having a computer network ?

Answer 8

• Increase computing power
• Increase system reliability by providing redundant processing
• Share data through network
• Share valuable resources
• To organize convenient interactions of users working at their own computers, often in different locations

Question 9

Give examples of client server relationships ?

Answer 9

• Email client like outlook communicating with a server
• Printing
• Web browsing via chrome/firefox/etc
• Facebook