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Operating Systems Contents What is an Operating System? Operating System Evaluation Operating System Design Some new components in the Operating Systems Operating Systems What is a house? The house is a dwelling place which enables people to use various facilities in comfort A house gives consistent services and interfaces, e.g. switches, taps, sockets, aerial leads, doors, windows... People (service users) House Hardware (e.g. power stations, satellites, water mains) Operating Systems What is an OS? The OS is a software system which sits between the hardware and the application software An OS give consistent services and interfaces, e.g. disc access, keyboard input, video output, memory management... Application Software Operating System Hardware Operating Systems Computing without an OS It is possible to ignore the OS and take over the hardware directly But software that does this is making life difficult for itself probably implementing its own internal OS anyway usually a game system which does not need a complex, full-featured OS to work Modern PC software uses the OS Operating Systems Computing with an OS Share the “processor power”… Share Resources E.g. Keep track of used and unused memory and drive space, arbitrate between demands on scarce resources Multitasking Run multiple programs in their own space, sharing resources Networking Communicate between computers even they have different hardware and software – standardised data formats OS often comes with a GUI – may be many choices of GUI Operating Systems Examples Big Computers Bespoke versions of Linux e.g. CLE for HECToR (a UK National Supercomputing Service resource - http://www.hector.ac.uk/) Servers Windows Server, MacOS, Linux – many versions of each Desk top computers Windows (based on Windows NT) MacOS (built on top of Unix) Linux (many varieties, many GUIs) Portable devices Android (built on Linux), Windows Mobile 8, IOS (built on Unix), Blackberry (based on QNX) Operating Systems Operating System Evolution The first computers had small quantities of memory limited processing abilities a highly restrictive interface (keyboard only) and monochrome displays Operating Systems Operating System Evolution To control the hardware and perform useful tasks, simple instructions had to be given These instructions took the form of typed sequences of commands This was the birth of the command-line interface (the CLI) An early but powerful version was UNIX (also available in a slightly different form as Linux for modern PCs) Operating Systems Loading the OS - BIOS v UEFI EFI (now UEFI) is a secure boot loader system that replaces the old BIOS approach Checks the NVRAM custom settings Loads only the signed interrupt handlers and device drivers Initializes registers and power management Performs the power-on self-test (POST) Displays system settings Determines which devices are bootable Initiates the signed OS start-up sequence Operating Systems Operating System Evolution - GUIs Most people are used to using a GUI (Graphical User Interface) to control a computer The GUI was invented in the early 1970’s at Xerox PARC (Palo Alto Research Center) Modern GUIs are derived from this first GUI A screen grab from Windows 3.1 Operating Systems Operating System Design The design of the operating system may be very closely tied to the hardware platform that it is to be run on Example: Older Blackberry & Nokia phone software It is possible to have a “hardware abstraction layer” to reduce the hardware-specific nature of an OS Example: Device drivers for Windows Look up “monolithic” and “micro-kernel” OSes Operating Systems Desktop Windows Manager Their drawing is redirected to off-screen surfaces in video memory, which are then rendered into a desktop image and presented on the display The contents of every open window is stored in video memory to facilitate movement of windows. Operating Systems Wide range of systems - Example There are 20 million cars on the road running QNX in various forms – for their real-time engine monitoring to their built in entertainment systems. Cars use technologies including entertainment and real-time monitoring, but are moving towards self-driving technology, parking guidance and networked entertainment and information systems All of this predicates a powerful OS Key players are Microsoft (Windows Embedded Automotive), Google (Android), Tizen [Samsung and Intel] (Linux), Audi (MMI) See: http://www.forbes.com/sites/parmyolson/2013/01/03/among-thehot-trends-for-ces-2013-cars-that-run-on-android/ Operating Systems Conclusion The “real-time OS” for “embedded systems” is an area of much development at the moment Example: the old Sega Dreamcast games console ran Windows CE OS (an early version of the MS Windows Mobile OS) Smart cards, engine management systems, mobile phones, Internet devices all run some kind of OS Wherever there is a CPU there is likely to be an OS of some type