What are the four types of Operating System and what type of device or system do they operate in?
- Desktop- PC’s.
- Server- Web servers, file server.
- IOS/Mobile- Phones.
- Real Time- Washing machines, cameras, etc.
Describe the key features of the Desktop OS.
- Runs on computers.
- Provides a disk file system.
- Provides user interface.
- Network support.
- Handles hardware devices.
- Allows running of software.
Describe the key features of the Server OS.
- 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.
Describe some key features of the IOS/Mobile OS.
- 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.
Describe key features of the Real Time OS.
- 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.
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?
- 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.
Describe FAT. (File allocation table).
- Separates files.
- Removes random access problem.
- Simple to implement, popular in small devices.
Describe Inodes.
- Used in *nix Systems.
- Only open files kept in memory.
- Linux uses Inodes.
Describe NTFS (New technology file system).
- Sophisticated file system.
- High levels of control and security.
- Mft controls operations in NTFS.
Describe what “virtual memory” is.
Give an advantage and a disadvantage.
-Allows more RAM usage through borrowing disk space.
Advantage: Allows loading of applications bigger than memory.
Disadvantage: Slower than pure RAM.
Describe the three task states:
“Running”
“Ready”
“Waiting”.
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.
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?
0-15- Dynamic Applications, less critical.
16-31- Real time processes, Critical.
0 is low priority, 31 is high.
Describe what a page is.
A page is a form of memory management, a chunk which can be swapped.
Pages are organised like pages in a book, very organised!
Describe a page table.
Also describe whata present bit shows, and what an accessed bit shows.
And what TLB is.
- 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.
