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1. Types of Operating System

2. Learning Objectives: By the end of this topic you should be able to: • Synoptic: describe the functions of an operating system • identify the major characteristics of different types of operating systems

3. What is an Operating System? • "A program or suite of programs that controls the entire operation of the computer" - BCS definition • the software responsible for allocating and managing system resources • memory, processor time, disk space • examples include: • Windows (Microsoft), • iOS (Apple) • Android (Google) • Linux (open source)

4. Why do we need an Operating System? • Computer system = Hardware + Software • application programs (software) communicate with system hardware via the operating system • so programmers can write software to run on an OS • not every type of hardware • different types of computer system will require different operating system features: • networked & single user PC • mobile 'phone, tablet computer, games console, • sat nav, TV, digital camera • …….

5. Functions of an Operating System • controlling computer hardware, • CPU, RAM, printers, disk drives, keyboard, mouse, touchscreen…. • organising files on storage media, • hard drive, CDROM, memory cards, memory sticks …. • providing the user interface • receiving commands from the system operator • e.g. to copy or delete files • security: detecting and preventing unauthorised use, • managing hardware errors • protecting data files and programs from corruption, • reporting and logging hardware and software usage & errors

6. Types of Operating System • SingleUser • Multi-user • Multi-tasking • Interactive • Real Time • Batch Processing • Distributed Systems

7. Single User • standard OS for a standalone computer systems • only one person can use the computer system at any one time • can support multiple accounts but only one used at a time • processing power of CPU dedicated to the user • so multi-tasking can be performed • i.e. running more than one program for that user at the same time

8. Multi User • more than one user accessing the system at the same time • most commonly: network operating system • server computer connected to a number of terminals • client-server LAN, ATM, ticket booking • O/S allocates a time slice to each user • switches from user to user • the larger the number of users the slower the system works • can run several programs simultaneously

9. Multi-Tasking • CPU carries out more than one task at the same time • several programs can be loaded and running at the same time • e.g. using a word processor whilst browsing the Internet • processor switches between tasks • completes part of one task then switches to do part of another task • this process happens very fast • appears that tasks are running concurrently • true multi-tasking requires more than one processor • many currentCPUs have multiple processing cores

10. Interactive • direct user interaction whilst a program is running • accepts and responds to input from user • "question and answer" between user and computer • computer gives the user an immediate response

11. Interactive Processing: Examples: • Booking concert tickets • Ordering books online • Handling bank accounts • Booking a holiday: • fill in a web form, • submit it • site informs you of the room you have booked.

12. Real Time • must respond to events with no discernible delay • responds immediately to the data entered • used where response time by the system is critical • where delays in processing would prove unacceptable • used for control systems • traffic lights, air traffic control, aircraft navigation • used for embedded systems • systems within another application, • e.g. cars and mobile phones

13. Real Time Examples: • Traffic lights • Heart rate monitoring • Aircraft control • Computer games • Controlling robots

14. Batch Processing: • data can be collected over a period of time • when all data collected it is processed at the same time • as a 'batch' • data is processed at an off-peak period • when there is less demand on the processor • less disruption to the daily work schedule • system & peripherals available when most needed • does not need staff intervention • suitable for situations where there is a lot of similar data to be processed & the processing can wait: • cheque processing in a bank, gas bill printing, payroll processing • not suitable where the data must be processed instantly • data is not up to date until processing completed

15. Distributed Systems • complex task split into a number of smaller, similar tasks • a series of computers connected together via network • computers can be in different physical locations • each computer performs part of the processing • results from individual machines are combined to achieve the overall task • Examples: • film animation & CGI via "render farms" • modelling real world scenarios – scientific, environmental, financial ……. • analysis of large datasets • List: http://en.wikipedia.org/wiki/List_of_distributed_computing_projects

16. Distributed Supercomputers

17. Dell Stampede • Dell PowerEdge C8220 server cluster • 96,000 processing cores, • 205TB of RAM memory, • 10 petaflops of peak performance • Intel Core i5 processor = 100 gigaflops • 1 petaflop = 1000 teraflops = 1 million gigaflops

18. PlayStation Supercomputer

19. PlayStation Supercomputer • 1,760 PS3 gaming consoles • among the 40 fastest computers in the world • 205TB of RAM memory, • 53 teraflops of peak performance • core i5 processor = 100 gigaflops • 1 teraflop = 1 million, million calculations per second (1012)