2 Learning Objectives: By the end of this topic you should be able to: Synoptic: describe the functions of an operating systemidentify 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 definitionthe software responsible for allocating and managing system resourcesmemory, processor time, disk spaceexamples include:Windows (Microsoft),iOS (Apple)Android (Google)Linux (open source)
4 Why do we need an Operating System? Computer system = Hardware + Softwareapplication programs (software) communicate with system hardware via the operating systemso programmers can write software to run on an OSnot every type of hardwaredifferent types of computer system will require different operating system features:networked & single user PCmobile ‘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 interfacereceiving commands from the system operatore.g. to copy or delete filessecurity: detecting and preventing unauthorised use,managing hardware errorsprotecting data files and programs from corruption,reporting and logging hardware and software usage & errors
6 Types of Operating System Single UserMulti-userMulti-taskingInteractiveReal TimeBatch ProcessingDistributed Systems
7 Single User standard OS for a standalone computer systems only one person can use the computer system at any one timecan support multiple accounts but only one used at a timeprocessing power of CPU dedicated to the userso multi-tasking can be performedi.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 systemserver computer connected to a number of terminalsclient-server LAN, ATM, ticket bookingO/S allocates a time slice to each userswitches from user to userthe larger the number of users the slower the system workscan 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 timee.g. using a word processor whilst browsing the Internetprocessor switches between taskscompletes part of one task then switches to do part of another taskthis process happens very fastappears that tasks are running concurrentlytrue multi-tasking requires more than one processormany 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 computercomputer gives the user an immediate response
11 Interactive Processing: Examples:Booking concert ticketsOrdering books onlineHandling bank accountsBooking a holiday:fill in a web form,submit itsite informs you of the room you have booked.
12 Real Time must respond to events with no discernible delay responds immediately to the data enteredused where response time by the system is criticalwhere delays in processing would prove unacceptableused for control systemstraffic lights, air traffic control, aircraft navigationused for embedded systemssystems within another application,e.g. cars and mobile phones
13 Real Time Examples: Traffic lights Heart rate monitoring Aircraft controlComputer gamesControlling robots
14 Batch Processing: data can be collected over a period of time when all data collected it is processed at the same timeas a ‘batch’data is processed at an off-peak periodwhen there is less demand on the processorless disruption to the daily work schedulesystem & peripherals available when most neededdoes not need staff interventionsuitable 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 processingnot suitable where the data must be processed instantlydata is not up to date until processing completed
15 Distributed Systemscomplex task split into a number of smaller, similar tasksa series of computers connected together via networkcomputers can be in different physical locationseach computer performs part of the processingresults from individual machines are combined to achieve the overall taskExamples:film animation & CGI via “render farms”modelling real world scenarios – scientific, environmental, financial …….analysis of large datasetsList:
19 PlayStation Supercomputer 1,760 PS3 gaming consolesamong the 40 fastest computers in the world205TB of RAM memory,53 teraflops of peak performancecore i5 processor = 100 gigaflops1 teraflop = 1 million, million calculations per second (1012)