2b Operating Systems

Roles
1. Deals with security and passwords
2. Responds to user input
3. Manages computer system
4. Opens and saves files
5. Allocates memory to applications
6. Communicates with hardware (using drivers)
7. Prioritises processes.
Single User
1. Only one user can use the computer system (processor) at a time.
2. There can be multiple user ACCOUNTS but they can't be used simultaneously.
3. e.g. A stand alone computer with no network connection
Multi-user
1. Can be used by more than one user at a time
2. e.g. Can refer to a networked server with many devices connected
3. e.g Can be a mainframe computer with many terminals
4. Roles
  1. Manage log-ons and permissions
  2. Allocate jobs
  3. Allocate memory to each user.
Multi-tasking
1. Can process more than one task at the same time
2. e.g. word processor being opened while a document is printing
3. Fast single processors can use scheduling to seem like their are multi-tasking
  1. Seems like multitasking
4. Processors with multiple cores of systems with more than one processor can really multi-task
Distributed processing
1. Processes using several processors from several computers usually in different locations
2. Computers need to be networked LAN or WAN
3. Every computer has its own processor and memory
4. One computer (usually a server) acts as co-ordinating device
  1. Server assigns tasks to other processors
    1. Result gathered by co-ordinating device to produce final output
5. Processing takes place when other processors are idle from normal task e.g. at night
6. e.g multi-player games or research applications

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