Computer Architecture

Front 1

CPU• ALU • CU • Registers

Back 1

Central Processing Unit • Arithmetic Logic Unit • Control Unit • small temporary storage spaces inside the CPU

Front 2

Function of the CPU

Back 2

The key component of a computer system,which contains the circuitry necessary tointerpret and execute program instructions

Front 3

Function of the ALU

Back 3

• 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

Front 4

Functions of the CU

Back 4

• 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.

Front 5

Von Neumann Architecture

Back 5

• 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

Front 6

4 most important registers.

Back 6

• MAR

• MDR

• Accumulator

• Program Counter

Front 7

Program Counter

Back 7

Holds the memory address of the next instruction.

Front 8

Accumulator

Back 8

Holds the intermediate results of the currently running instructions.

Front 9

MAR (Memory Address Register)

Back 9

• Connected to the address bus.

• Contains a memory address.

• Contains the RAM address of the instruction the CPU wants next.

Front 10

MDR (Memory Data Register)

Back 10

• 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.

Front 11

RAM (Random Access Memory)

Back 11

• 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

Front 12

ROM (Read Only Memory)

Back 12

• 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.

Front 13

Bus

Back 13

A set of wires that connect two components in a computer system.

Front 14

Cache

Back 14

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.

Front 15

Machine Instruction Cycle

Back 15

Fetch, decode, execute, store.

Front 16

Why we need ‘storage’?

Back 16

• Processingdone in CPU, has nostorage

• Storesresults/data inRAM, RAM is volatile

• Needs to bestored onpersistentstorage HDD/SSD.

Front 17

Functions of an operating system

Back 17

• Provides a user interface

• Does memory management

• Does peripheral management

• Allows multi-tasking

• Provides security

Front 18

User interface

Back 18

OS has to provide a link between the user and thecomputer hardware.

Front 19

Types of UI

Back 19

• 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.

Front 20

Memory management

Back 20

• 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.

Front 21

Peripheral management

Back 21

• 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.

Front 22

Multitasking

Back 22

• 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.

Front 23

Security

Back 23

• OS prevents unauthorised access.

• It ensures security of the system throughusernames and passwords.

• The OS protects files from other users reading orwriting files.

Front 24

Common application software

Back 24

• Word processors

• Spreadsheets

• DBMS

• Email clients

• Web browsers

• Computer Aided Design (CAD)

• Graphic Processing Software

Front 25

Word Processor (not just Word!)

Back 25

A program for storing, manipulating, and formatting text entered from a keyboard and providing a printout.

Front 26

Spreadsheet (not just Excel!)

Back 26

A program in which data is arranged in the rows and columns ofa grid and can be manipulated and used in calculations.

Front 27

DBMS

Back 27

A system software forcreating and managing databases. The DBMS provides usersand programmers with a systematic way to create, retrieve,update and manage data.

Front 28

Email clients (not webmail like Gmail!)

Back 28

A computer program used to access and manage a user's email.

Front 29

Web browser

Back 29

A software application for retrieving, presenting, and traversing information resources on the World Wide Web.

Front 30

Computer Aided Design (CAD)

Back 30

Programs that use computer systems to assist in the creation, modification, analysis, or optimization of a design.

Front 31

Graphic Processing Software

Back 31

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.

Front 32

Common features of most programs are

Back 32

• Toolbars

• Menus

• Dialogue Boxes

• GUI components

Front 33

OS vs Application features

Back 33

• 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