Operating systems

Question 1

What are the four types of Operating System and what type of device or system do they operate in?

Answer 1

1. Desktop- PC’s.
2. Server- Web servers, file server.
3. IOS/Mobile- Phones.
4. Real Time- Washing machines, cameras, etc.

Question 2

Describe the key features of the Desktop OS.

Answer 2

• Runs on computers.
• Provides a disk file system.
• Provides user interface.
• Network support.
• Handles hardware devices.
• Allows running of software.

Question 3

Describe the key features of the Server OS.

Answer 3

• Dedicated to producing services to users, such as web servers or gaming servers, etc.
• Server OS are optimised to run software and systems, Desktop OS can too but not as effectively.
• Optimised for multiple user requests.
• Not optimised for direct user interaction.

Question 4

Describe some key features of the IOS/Mobile OS.

Answer 4

• Used on mobile devices.
• Optimised for limited hardware resources.
• Supports application specific tasks, such as user location.
• Lack of sophisticated features compared to desktop OS.

Question 5

Describe key features of the Real Time OS.

Answer 5

• Prevalent among systems such as cameras and washing machines, everyday machines which need operating systems.
• Use little memory or resources.
• Provide a quick response to real time signals.

Question 6

Both file allocation systems “Continuous allocation” and “Linked lists” will encounter an issue known as fragmentation. What is this and how does it affect both systems?

Answer 6

• Continuous allocation: Erased files leave gaps of varying sizes. Results in multiple gaps.
• Linked lists: No need to find gap, any gap will do. Fragmentation is exaggerated; parts of file are scattered, so seeking a file takes time.

Question 7

Describe FAT. (File allocation table).

Answer 7

• Separates files.
• Removes random access problem.
• Simple to implement, popular in small devices.

Question 8

Describe Inodes.

Answer 8

• Used in *nix Systems.
• Only open files kept in memory.
• Linux uses Inodes.

Question 9

Describe NTFS (New technology file system).

Answer 9

• Sophisticated file system.
• High levels of control and security.
• Mft controls operations in NTFS.

Question 10

Describe what “virtual memory” is.

Give an advantage and a disadvantage.

Answer 10

-Allows more RAM usage through borrowing disk space.

Advantage: Allows loading of applications bigger than memory.

Disadvantage: Slower than pure RAM.

Question 11

Describe the three task states:
“Running”
“Ready”
“Waiting”.

Answer 11

Running: Currently being executed.

Ready: Not being executed but is prepared to be executed.

Waiting: task won’t run due to not being prepared or ready.

Question 12

Windows uses a number range to set priority of tasks. What is the range of numbers and what kind of tasks falls within each range?

Answer 12

0-15- Dynamic Applications, less critical.

16-31- Real time processes, Critical.

0 is low priority, 31 is high.

Question 13

Describe what a page is.

Answer 13

A page is a form of memory management, a chunk which can be swapped.

Pages are organised like pages in a book, very organised!

Question 14

Describe a page table.

Also describe whata present bit shows, and what an accessed bit shows.

And what TLB is.

Answer 14

• A list of pages and their addresses.
• “Present bit” shows whether Data is in RAM or not.
• “Accessed bit” shows if page has been used or not.
• “Translation lookaside buffer” (TLB) acts as a cache for page tables.