Operating System

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Operating System by Mind Map: Operating System

1. Main Objective

1.1. Convenience

1.1.1. makes a computer more convenient to use

1.2. Efficiency

1.2.1. allows the computer system resources to be used in an efficient manner

1.3. Ability to evolve

1.3.1. should be constructed in such a way as to permit the effective development , testing , and introduction of new system functions without interfering with service

2. Evolution of OS

2.1. Evolve over time for a number of reasons

2.1.1. hardware upgrades

2.1.2. new types of hardware

2.1.3. new services

2.1.4. Fixes

2.2. Stages include

2.2.1. Serial Processing

2.2.2. Simple Batch Systems

2.2.3. Multiprogrammed Batch Systems

2.2.4. Time Sharing Systems

3. Serial Processing

3.1. Earliest Computers

3.1.1. No operating system

3.1.2. Users have access to the computer in “series”

3.2. Problems

3.2.1. Scheduling

3.2.2. Setup time

4. Simple Batch Systems

4.1. Early computers were very expensive

4.1.1. important to maximize processor utilization

4.2. Monitor

4.2.1. user no longer has direct access to processor

4.2.2. program branches back to the monitor when finished

5. Point of View

5.1. Monitor

5.1.1. controls the sequence of events

5.1.2. Resident Monitor is software always in memory

5.1.3. reads in job and gives control

5.1.4. Job returns control to monitor

5.2. Processor

5.2.1. executes instruction from the memory containing the monitor

5.2.2. Executes the instructions in the user program until it encounters an ending or error condition

5.2.3. control is passed to a job

5.2.3.1. processor is fetching and executing instructions in a user program

5.2.4. control is returned to the monitor

5.2.4.1. processor Is fetching and executing instructions from the monitor program

6. Simple Batch System Overhead

6.1. Processor time alternates between execution of user programs and execution of the monitor

6.2. Sacrifices

6.2.1. some main memory is now given over to the monitor

6.2.2. some processor time is consumed by the monitor

6.3. Despite overhead, the simple batch system improves utilization of the computer

7. Time-Sharing Systems

7.1. Can be used to handle multiple interactive jobs

7.2. Processor time is shared among multiple users

8. Parallel Systems

8.1. Multiprocessor systems with more than one CPU in close communication.

8.2. Tightly coupled system

8.2.1. processors share memory and a clock; communication usually takes place through the shared memory.

8.3. Advantages

8.3.1. Increased throughput

8.3.2. Economical

8.3.3. Increased reliability

9. Symmetric Multiprocessing (SMP)

9.1. refers to a computer hardware architecture and also to the OS behavior that exploits that architecture

9.2. Several processes can run in parallel

9.3. Multiple processors are transparent to the user

9.3.1. processors share same main memory and I/O facilities

9.3.2. all processors can perform the same functions

10. Asymmetric Multiprocessing (SMP)

10.1. Each processor is assigned a specific task

10.2. More common in extremely large systems

11. Distributed Systems

11.1. Distribute the computation among several physical processors.

11.2. Loosely coupled system

11.2.1. each processor has its own local memory; processors communicate with one another through various communications lines, such as high-speed buses or telephone lines.

11.3. Advantages

11.3.1. Resources Sharing

11.3.2. Computation speed up

11.3.2.1. load sharing

11.3.3. Reliability

11.3.4. Communications requires networking infrastructure.

12. Real-Time Systems

12.1. operating system, and in particular the scheduler, is perhaps the most important component

12.2. Examples

12.2.1. control of laboratory experiments

12.2.2. air traffic control

12.2.3. process control in industrial plants

13. Hard and Soft Real-Time Tasks

13.1. Hard real-time task

13.1.1. one that must meet its deadline

13.2. Soft real-time task

13.2.1. has an associated deadline that is desirable but not mandatory

14. Real Time Systems

14.1. five general areas

14.1.1. Determinism

14.1.2. Responsiveness

14.1.3. User control

14.1.4. Reliability

14.1.5. Fail-soft operation

15. Determinism

15.1. Concerned with how long an operating system delays before acknowledging an interrupt

15.2. Operations are performed at fixed, predetermined times or within predetermined time intervals

16. Responsiveness

16.1. Together with determinism make up the response time to external events

16.2. Concerned with how long, after acknowledgment, it takes an operating system to service the interrupt

17. User Control

17.1. Generally much broader in a real-time operating system than in ordinary operating systems

17.2. It is essential to allow the user fine-grained control over task priority

17.3. User should be able to distinguish between hard and soft tasks and to specify relative priorities within each class

18. Reliability

18.1. More important for real-time systems than non-real time systems

19. Fail-Soft Operation

19.1. characteristic that refers to the ability of a system to fail in such a way as to preserve as much capability and data as possible