Fundamentals

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1. INPUT Much conversion of language occurs in a computer system

(English)

DATA INPUT DEVICE

(binary)

CPU

(binary)

OUTPUT DEVICE INFO

(English)

Input/ OutputInput/ Output

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Two types of input : Data and InstructionsTwo types of input : Data and Instructions

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Input DevicesInput Devices

Provides:-entry of data-Conversion into data format

Most obvious = human + KEYBOARD

Human data entry is called non-direct input.Machines make better input devices.

DIRECT ENTRY, or SOURCE DATA AUTOMATION.

Need to be: Accurate, reliable and easy to

use, fast

Human and keyboard is the most used input device

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Examples of Direct Entry Input DevicesExamples of Direct Entry Input Devices

- flat bed or hand-held- Similar to a photocopier- Reads page as a grid of dots- stores data as a "picture" MICR : Used with cheques

Scanners

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Examples of Direct Entry Input DevicesExamples of Direct Entry Input Devices

Barcode Readers:

Sit-in-the-Counter type - Reads standard or customised barcodes- Can also purchase software to print barcodes.

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Input TypesInput Types

a.

Data Collection Devices:Stocktake devicesAutomatic counters

Web CamsVideo camera whose output displays on a web page

Digital Camera

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Other Input DevicesOther Input Devices

a.

Sensors-Encode a physical event into data

Pointing DevicesMouse

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Other Input DevicesOther Input Devices

TouchPadPointing StickLight Pen

Trackball

• Similar to mouse

Joystick• games

Touch screens• screen 'divided' into areas• area selected by touch• easy to use• cannot have areas too small• screens get dirty (many uses)

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Voice InputVoice Input

Voice Input• hands free• trained for each voice

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OutputOutput

Four common type of output are text, graphics, audio and video.

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OutputOutput

Output Devices

Digital signals from computer are converted into human readable form.

Hard Copy - printer- plotter

Soft Copy- screen- voice

PrintersImpact printers•Impact a solid image of a character onto an inked ribbon up against the paper.

Non-impact printers• no physical contact between paper and printing device• dot matrix concept used to form characters

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OutputOutput

Ink jet• quiet

Thermal• special paper• expensive to run

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OutputOutput

Laser• high speed, high quality• page printers• need enough memory to hold an entire page• 600 to 2400 dpi

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OutputOutput

CRT Monitors

•Raster scan technology

•An electron beam moves back and forward across the back of the screen

•This causes dots on the front of the screen to glow, producing an image

•Available in various sizes 15 – 22 inches

•Flat and curved screens

Resolution

•Increase pixels/screen

•Increase resolution (better image)

•CRT monitors ( 1280 X 1024 pixels)

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OutputOutput

LCD Monitors•Contains liquid crystals between 2 sheets of material

•An electric current passes through the crystals causing them to twist, block light waves and create an image.

•Uses less than one third the power of a CRT monitor

•Lightweight and compact (mobile users)

Gas Plasma Monitors

•A layer of gas instead of liquid crystals

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Other Output DevicesOther Output Devices

Data Projectors

Fax Machine

•Transmits and receives documents over the telephone line

Multifunction devices

•Printer, scanner, copy machine and fax machine all in one

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SECONDARY STORAGESECONDARY STORAGE

Control Unit works on programs/data in RAMPOWER OFF ... RAM OFFBye Bye AssignmentHowever blocks of memory can be saved/read on secondary storage.

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Secondary Storage Media and Devices

Floppy DisksHard DisksTape and Tape driveCartridge tapeCD-ROMDVD ROMMagnetic-Optical drivePC CardsSmart Cards

SECONDARY STORAGESECONDARY STORAGE

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FLOPPY DISKS:FLOPPY DISKS:

• Circular piece of plastic• Made up of tracks & sectors• 512 bytes in each sector

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Maintaining data stored on a disk

• Made up of platters, cylinders and sectors• head 'floats' on surface• capacities range up to 200+ GB

HARD DISKSHARD DISKS

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OPTICAL STORAGE TECHNOLOGY• high capacity is ideal for storage of the very large sound, graphics and video files• when recording data, laser light burns pits on CD• when reading data, pits will not reflect light (binary bit 0) but lands will reflect light (binary bit 1)

CD-ROM (compact disk read-only memory)- 650 MB of information

DVD (digital video disk) - 4.7 GB – 17 GB

Hard Disk Vs Floppy Disk

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Optical Storage

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Optical Storage

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TAPE

• Thin ribbon of plastic• Sequential storage – mainly for backup

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OTHER TYPES OF STORAGE DEVICESOTHER TYPES OF STORAGE DEVICES PC cardsPC cards

• Small, credit card-sized cards that fit into PC Card expansion slots •Used for storage, communications and additional memory.• Most often used with portable computers• Can store more than 300 MB of data

Smart Cards• Credit card-sized devices that contain a microprocessor• Microprocessor can store up to 8,000 bytes of information.• Examples of uses - prepaid telephone card, employee time card

USB Drive•Flash memory storage device that plugs in a USB port

•Small and lightweight