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33 Cards in this Set
- Front
- Back
CPU• ALU • CU • Registers |
Central Processing Unit • Arithmetic Logic Unit • Control Unit • small temporary storage spaces inside the CPU |
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Function of the CPU |
The key component of a computer system,which contains the circuitry necessary tointerpret and execute program instructions |
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Function of the ALU |
• Part of the CPU that does all the arithmetic and logical calculations • Sometimes referred to a ‘core’. • Computerswith dual core technology have two ALUs to process twocalculations simultaneously |
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Functions of the CU |
• It handles the loading of new commands intothe CPU and the decoding of these commands. • Also, it directs the data flow and the operationof the ALU. |
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Von Neumann Architecture |
• Von Neumann Architecture suggests that acomputer system be split in to a processor module and a memory module. • We still use this model today: CPU and Primary Memory |
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4 most important registers. |
• MAR • MDR • Accumulator • Program Counter |
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Program Counter |
Holds the memory address of the next instruction. |
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Accumulator |
Holds the intermediate results of the currently running instructions. |
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MAR (Memory Address Register) |
• Connected to the address bus. • Contains a memory address. • Contains the RAM address of the instruction the CPU wants next. |
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MDR (Memory Data Register) |
• Connected to the data bus. • Holds data that will be written to/read from the RAM. • Relationship between MAR & MDR: The MAR gives theaddress the data of the MDR will be read from or written to. |
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RAM (Random Access Memory)
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• Contains the data and instructions thecomputer has loaded since starting up andeverything the user has opened/loaded. • Is volatile = loses its contents if power is lost |
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ROM (Read Only Memory) |
• Originally its contents were static andcould not be changed – you can now, using flashupgrades. • Non-volatile • Stores the BIOS (Basic Input Output System) – a smallprogram that allows the computer to know what to do tofind the operating system to ‘boot’ the computer afterpower is restored. |
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Bus |
A set of wires that connect two components in a computer system. |
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Cache |
A type of small, high-speed memory inside theCPU used to hold frequently used data, so thatthe CPU needs to access the much slower RAMless frequently. |
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Machine Instruction Cycle |
Fetch, decode, execute, store. |
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Why we need ‘storage’? |
• Processingdone in CPU, has nostorage • Storesresults/data inRAM, RAM is volatile • Needs to bestored onpersistentstorage HDD/SSD. |
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Functions of an operating system |
• Provides a user interface • Does memory management • Does peripheral management • Allows multi-tasking • Provides security |
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User interface |
OS has to provide a link between the user and thecomputer hardware. |
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Types of UI |
• Graphical User Interfaces (GUIs) that have menus andicons • Natural Language Interface (NLIs) where the user speaks to the interface • Command Line Interfaces (CLIs) where the user types in codes • Menu Based Interface (MBIs) which gives the user aselection of options. |
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Memory management |
• Memory management is done by keeping track ofstorage devices and controlling whichapplication has access to which area of memory(RAM). • Each location in memory can be read, modified, andwritten to by the OS. When the memory location is fullthe OS sends a confirmation message. • Similarly, the OS provides file management services bysorting out where data is stored on the disk drives andmemory. • The OS allows users to organise files in folders as well asto copy and delete files. |
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Peripheral management |
• The OS coordinates the BIOS. • Keyboard, mouse, monitorand printers are controlledthrough device drivers. • A device driver is a softwareprogram which allowshardware devices to beused by the OS. They act astranslators between thedevices and the computersystem. |
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Multitasking |
• The OS coordinates the working of different programsby allocating the CPU time between different programsbased on time and priority of the software application. • Each task running is given a slice of time, or a turn onthe CPU. • Each task has to wait its turn unless it is given a higherpriority by the OS in which case it gets more or longertime slices. |
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Security |
• OS prevents unauthorised access. • It ensures security of the system throughusernames and passwords. • The OS protects files from other users reading orwriting files. |
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Common application software |
• Word processors • Spreadsheets • DBMS • Email clients • Web browsers • Computer Aided Design (CAD) • Graphic Processing Software |
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Word Processor (not just Word!) |
A program for storing, manipulating, and formatting text entered from a keyboard and providing a printout. |
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Spreadsheet (not just Excel!) |
A program in which data is arranged in the rows and columns ofa grid and can be manipulated and used in calculations. |
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DBMS |
A system software forcreating and managing databases. The DBMS provides usersand programmers with a systematic way to create, retrieve,update and manage data. |
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Email clients (not webmail like Gmail!) |
A computer program used to access and manage a user's email. |
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Web browser |
A software application for retrieving, presenting, and traversing information resources on the World Wide Web. |
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Computer Aided Design (CAD) |
Programs that use computer systems to assist in the creation, modification, analysis, or optimization of a design. |
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Graphic Processing Software |
In computer graphics, graphics software or image editingsoftware is a program or collection of programs that enable aperson to manipulate visual images on a computer. |
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Common features of most programs are |
• Toolbars • Menus • Dialogue Boxes • GUI components |
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OS vs Application features |
• Certain parts of the interface are provided by libraries in theOS and certain parts are specific to each application • For example: the menu bar and buttons are standard, butthe specifics/pictures are up to the individual application |