A computer is an information processing machine.A computer only follows the instructions it is given.Data is Input, Processed and then Output.

What is a Computer?

I’m ONLY a machine!

Two types of data - Analogue and Digital

Analogue data can be of a wide range of values.Examples are: Temperature, Noise Level, Speed.

Digital information is stored in blocks.Examples are On/Off; Population

Data and Information

Data has no meaningData is made up of symbols e.g.871652; H789 IOS; £76.91

Information has a meaningWe understand what a piece of information is about e.gTelephone Number: 871652Car License Plate: H789 IOS

IPO - Input, Process, Output

INPUT PROCESS OUTPUT

Data is INPUT into the computer system

It is then PROCESSED to produce useful Information as OUTPUT.

Standalone Computer System

A system is a collection of parts that work together.A standalone computer system is a computer system that is NOT connected to other computers.It consists of at least one input device, a processor and one output device.The Central Processing unit contains the processor and main memory.Programs and data are stored in main memory

Types of Media

Media is the material used in devices.Examples of media are Floppy disc and CD-ROM.If CD-ROM is the MEDIA then the CD-ROM drive is the DEVICE.

Devices

Devices are either INPUT, OUTPUT or BACKING STORAGE.Input devices allow us to enter data into the computer system (mouse, microphone etc).Output devices allow us to receive information from the computer system (monitor, speakers, robot).Backing storage devices allow us to store programs and data so that we can use them later (floppy disc drive, magnetic tape drive , CD-ROM drive).

Hardware and Software

Hardware refers to all the parts of the Computer System that we can touch.Examples of hardware are monitors, joysticks, printers.Software refers to all the programs and data that we use with the computer.

Input DevicesMouse

A device which allows a computer user to move the screen cursor or pointer. A mouse usually has one or more buttons on top, a ball on the bottom and a cable connecting the mouse to the computer. Movement of the mouse causes a relative change in cursor location. Clicking the button causes a screen item or command to be selected.

KeyboardSimilar to a typewriter, contains the letters for typing text, and keys that give the computer its commands.

Touch Sensitive ScreenA Touch Sensitive Screen is a pointing device that enables the user to interact with the computer by touching the screen.

Input Devices

TrackballA trackball is basically an upside down mouse. A trackball allows the user to move a small ball in order to move the pointer across the screen.

TrackpadA trackpad mouse is a touch sensitive surface. The user places a finger on the surface and when the finger moves across the surface the mouse also moves.Trackpads are more commonly referred to as Glidepoint mice.

Input Devices

Graphics TabletA graphics tablet allows the user to draw on a special worktop. As the user draws the details are stored on the computer system. These devices are most often used by architects and designers.

JoystickJoystick is a term used for the handhold tool used in many computer-based video games. The joystick is designed after the steering stick of military airplanes, allowing movement in all four directions as well as rotational movement. In addition, buttons with certain functions can be located at several positions on the joystick.

Output Devices

VDUVisual Display Unit (VDU) is the proper name for the computer monitor. The VDU allows us to see the output from the computer.

PlotterA plotter is a device used for creating a hard copy of the output from a computer system. Plotters use special pens to draw the output as a series of lines. Plotters are often used to output building drawings and designs.

Output Devices

PrintersLaser Printer

• A type of printer that uses a laser beam to produce an image on a drum and then ink dust (toner) sticks to the image. This dust is pressed onto paper and then heated to make it stick.

The resolution of printers and other output devices can be measured in dots-per-inch (dpi).

Output Devices

PrintersInkjet Printer

• A printer mechanism that sprays one or more colours of ink onto paper and produces high-quality printing. A typical black ink cartridge contains a print head with up to 144 nozzles. Each nozzle is responsible for a single dot of ink.

An inkjet cartridge

Output devices

Laser printerExpensive to buyHigh quality output

Very quick to print a pageRelatively low cost of tonerPrints quietlyColour models expensive and most costly to run

Inkjet printerCheap to buyGood quality output (but not as good as laser)Slow to print a page

Relatively high cost of new ink cartridgesQuiet, but noisier than laserRelatively cheap colour printing when compared to laser colour printing.

Comparison of Laser with Inkjet

Backing Storage Devices

Magnetic TapeA data storage medium used for backup. The tape is made of a thin plastic strip with a magnetic oxide coating on one side. To read or write, the tape drive winds the tape from one reel to another, causing it to move past a read/write head.

Floppy diskThe floppy disc was the main type of data storage used for many years but has been replaced by larger capacity USB Sticks and other removal media (such as Zip disc and flash cards). A floppy disc can store 1.44 Mb of data – the smallest USB Sticks hold approximately 32Mb.

Hard discA high capacity storage device inside your PC. Often known as drive C: although many computers may also have a drive D:. The hard drive disks are most often made from machined aluminium and have a similar magnetic coating painted on them that the floppy disk has.

Backing Storage Devices

Using disks and making backups

A floppy disc is used to save data.It can be used to make a backup copy of small files.A backup is a second copy of your data that you take in case something happens to the original.The original might get -

LostCorrupted (i.e. made unreadable)DamagedStolen

You should always make a backup of important files.And don’t keep the backup in the same place as the original copy!

Write Protect TabDisc Label

Format and Copy Discs

New discs must be formatted for the type of Computer System that they will be used in.Files can be copied to floppy disc to create backup copies.To format a floppy disc in Windows.Double click the ‘My Computer’ Icon.Insert the floppy disc to be formatted.Right click ‘3½ Floppy [A]’ IconLeft click ‘Format..’Click ‘Full’ to carry out a full format of the Disc (‘Quick’ just erases an already formatted disc)Click ‘Start’ to format your disc. A message will be displayed when the format is finished.

Copying to a Disc (Windows)

Locate the files you want to copy.Select the files to be copiedLeft click Edit in the Window menu toolbar.Left click ‘Copy’Double click the 3½” Floppy [A] icon.Left click Edit in Window menu toolbar.Left click Paste. The files will be copied to the floppy disc.

Backing Storage Devices

CD-ROMA standard medium for storage of digital data, read with a laser-based reader. CDs are 12cms in diameter. CD-ROMs are manufactured with data on them – the data is pressed into the plastic using a special digital mould. CD-ROMs are never written onto (they are different from CD-R and CD-RW formats). Capacity 650 Mb or 74mins of music.

DVD-ROMDigital Versatile Disc Read Only Memory. Similar to a CD-ROM, it uses DVD technology to pack up to 25 times the information found on a CD-ROM. DVD-ROM drives can also play DVD movies and other high quality multimedia. Capacity: up to 8.5 Gb

Computer Networks

A network is made up of two or more computers linked together.Advantages are:

• Share devices between computers• Share data between computers• Share programs between computers• Saves time

A typical Local Area Network

A local area network is a computer network across one building or site.

Fileserver

Printer

Work Station

Network Cable

Types of Computers

Microprocessor– A small chip programmed with instructions.

Palmtop– A computer small enough to fit in the user's

hand. Primarily used as personal organisers.

Laptop– A small, portable computer -- small enough that

it can sit on your lap. A laptop computer can be called a notebook computer.

Desktop– A desktop computer is personal computer that

can fit on an end user's desk and perform business computing tasks. Also, especially if linked to a network of other computers, it may be referred to as a workstation.

Smallest

Biggest

Bits and Bytes

The computer is a digital machine.All data in the computer is stored digitally.Digital data in the computer is stored as zeros and one (called binary) e.g.

Binary01

1011

100101110111

1000

Decimal012345678

More Bits and Bytes

Each 1 or 0 is called a BIT (short for Binary Digit).Eight bits are called a BYTE.1024 (roughly 1000) bytes is a KILOBYTE (Kb for short)1024 kilobytes is a MEGABYTE (Mb for short)1024 megabytes is a GIGABYTE (Gb for short)1024 gigabytes is a Terrabyte (Tb for short)

These units are used to measure the size of storage (called CAPACITY) or storage requirements e.g. the available memory, hard disk space, program size.

Computer System - Block Diagram

The Computer System consists of four parts.Input, Processor, Output, Backing Storage

Processor OutputInput

BackingStorage

Data Flow

What is the CPUCPU - Central Processing UnitIt is the combination of the Processor and Memory.There are TWO types of memory in the CPU, RAM and ROM.

RAM ROM

PROCESSOR

Data Flow

Central Processing Unit

RAM and ROM

RAM is Random Access MemoryIt can be written to and read from. It is where most programs and data are stored while the computer is being used.

ROM is Read Only MemoryData stored in ROM can only be read, it can never be written over or deleted. We normally store important programs in ROM to do with the computers Operating System (see later).

Storing Numbers

Numbers are stored in binary.1Bin is 1Dec

10Bin is 2Dec

1000Bin is 8Dec

1001Bin is 9Dec

1111Bin is 15Dec

11111111Bin is 255Dec

You don’t need to understand binary (that’s Maths) but you do need to know that it is how most numbers are stored in the computer.

Storing GraphicsBlack and White graphics as stored using pixels (Picture Elements).The image to be stored is broken up into dots, each dot is a pixel.The pixels are ON for black and OFF for white e.g.

1 0 0 0 0 0 0 11 0 1 0 0 1 0 11 0 1 0 0 1 0 10 0 0 0 0 0 0 00 0 0 1 1 0 0 00 1 0 0 0 0 1 00 1 1 1 1 1 1 00 1 1 1 1 1 1 0

Storing TextText is stored using a special set of codes called ASCII.Each symbol (letter, number etc) has its own unique code e.g. a is 97, A is 65, ? is 63, 3 is 51ASCII (American Standard Code for Information Interchange)One ASCII code is one byte long (eight bits).

Capacity

The size of memory, hard disc space, floppy drive space, programs, data files etc. are all measured by the number of bytes, kilobytes, megabytes or gigabytes (1024 megabytes) they can store.

445 floppy discs

=1 CD-ROM

More on Memory

Computers store blocks of data called ‘words’ in memory (A 32 bit computer has words that are 32 bits long).Each place that can store a word is called a storage location.Each storage location has a unique address that identifies it from all the other locations.

Types of Computer

Mainframe ComputerA very large computer capable of supporting hundreds/thousands of users running a variety of different programs at the same time. Typically used by large businesses and for scientific purposes.

What is software

Software is the term that we use for all the programs and data that we use with a computer system.

Two types of softwareProgram - the instructions that the computer follows (e.g. a word processor or a game).Data - what the programs process (e.g. a word processing document or a saved game file)

Machine Code

Computers only understand binary codes.This means that ALL the programs that a computer carries out must also be in binary code.The binary language that a computer processor can understand is called MACHINE CODEMachine code is DIFFERENT for each type of processor – Apple Mac computers use a different processor and therefore a different machine code from PCs.

Low Level Languages

Computers only understand binary!!!All programs have to end up in binary language in order work.The binary language that the computer understands is called MACHINE CODEMachine code looks like this…

00100111,01110100,10010001

NOT very easy to understand.That’s why High Level Languages have been produced...

High Level Languages

We use high level languages (HLLs) because programming in machine code is VERY difficult.High level languages make it easier for us to write programs because we can use commands that mean something (PRINT, END, IF, THEN).High level language programs still have to be translated into machine code to work. This is done by a translator.There are lots of different HLLs but they all still have several things in common...

Common features of High Level Languages

English like words and phrases as instructions eg. PRINT, IF, THEN, END, STOP, ELSE, OPEN etc.Arithmetic operations such as multiply, divide, add subtract etc.

High level languages are problem orientated. This means that the programmer can forget about the internal workings and set-up of the computer system and can concentrate on solving the problem.

Common features of High Level Languages

Words and symbols are combined to conform to a predefined SYNTAX to produce program instructions (also called statements). Syntax are the rules which govern how the program commands are used (similar to the rules of grammar that govern how we use the English language). Must be translated into machine code. A special program (a type of systems software) called a translator does this….

Types of High Level Language

General purposeGeneral purpose high level languages are written for a wide variety of tasks. They can be used for any type of application however they may lack certain commands that make particular tasks easy to do.Special PurposeSpecial purpose high level languages are written for particular types of task. For example Delphi is written for windows database programming and has special commands that make this type of task easier to carry out.

OS - Different modes of processingThere are several different modes of processing.

InteractiveAccepting input from a human. Interactive computer systems are programs that allow users to enter data or commands. Most popular programs, such as word processors and spreadsheet applications, are interactive. In interactive processing, the application responds to commands as quickly as it can once they have been entered. Sometimes there is a delay while the processor finishes another task.

Real TimeReal-time operating systems are systems that respond to input immediately. Automatic teller machines for banks are an example of real time processing. Real time systems are used for tasks such as navigation, in which the computer must react to a steady flow of new information without interruption.

More Input Devices

ScannerA scanner is used to take information stored on paper and read it into a computer system. Scanners can be used to convert photographs, paintings etc. or even typed text into a form that can be stored on a computer.

Digital Still CameraA digital still camera looks and behaves like a regular photographic camera, except instead of using film, it stores the image it sees in memory as a file for later transfer to a computer. Many digital cameras offer additional storage besides their own internal memory; most use some sort of memory stick or card.

More Input Devices

Digital Video CameraA digital video camera takes stores video on digital tape, disc or memory card. The video is stored in a digital format.The video can then be easily transferred to a computer for editing.

Webcama digital camera designed to take digital photographs and/or video and transmit them over the internet