Introduction to Computers

IT Preparatory CourseDiploma in NursingUnity College International

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Are you a beginner

With computers? This course will helps you learn about

computers in an easy, friendly way

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Compare a computer

To a workshop such as Woodshop Kitchen

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Typical workshop features

Materials Tools Working Area Storage Measurements (may be English or

metric)

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Woodshop

Materials: Wood Tools: Hammer, saw, drill… Work area: Worktable Storage: Cabinet Measurements Yards, feet, inches,

meters, centimeters, millimeters

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Kitchen

Materials: Food Tools: Stove, mixer, spoon… Work Area: Counter, cutting board,

bowl… Storage: Refrigerator, cabinet… Measurements: Cups, tablespoons,

teaspoons, ounces pints, grams, liters

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Computers

How does this apply to computers? You will find materials, tools, work

area, storage, and measurements

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Computer Materials

Information Words Numbers Pictures

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Computer Tools

Two kinds: Hardware

Physical parts to computer Software

Instructions This slide show for example

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Computer Working Area

The work area of a computer is called a window.

The next slide shows a typical window.

You will use some windows in the last part of this class and in future classes.

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Typical Window

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Computer Storage

Two main types: Memory Data Storage

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Memory Often called RAM (Random Access

Memory) Information while you work on it

(like food while you eat it) Usually temporary (easily lost)

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Data Storage Information stored away for use later on

(like food in the refrigerator) Usually long-term (safer) May be stored on disks, CDs. DVDs, or

flash drives

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Measuring Information

Bytes One character takes up about one Byte. An email takes up a few (thousand

bytes) Kilobytes (thousands of bytes) A picture may take up Megabytes

(millions of bytes) All the information on a computer may

run into Gigabytes (billions of bytes)

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Storage Examples

Email, about a thousand characters Picture of granddaughter, about half a megabyte

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Hardware

Central Processing Unit (cpu) Brains of a computer

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Disks Floppy Disk

Main disk used for library users

Holds 1.44 Megabytes 1,440,000

Bytes Feels hard

Floppy part inside cover

Almost obsolete

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Hard Disk Main disk for

most computers

Holds Windows, software, and most data

Usually don’t see it because it’s inside computer.

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CD-ROM Uses optical

(laser) technology instead of magnetic

Holds large amount of data

Same technology as a music disk.

Not available on library computers

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Disks Disk geometry may vary

Different disks may have different number of sectors per track

Hide these details using a virtual geometry presented to the OS

Virtual geometry defined by x cylinders, y heads, and z sectors per track

Disk controller maps virtual to real geometry

Alternative: logical block addressing disk sectors numbered consecutively starting

at 0 No limits on number of sectors (depending)

Sectors and Tracks

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Overview of Computer Hardware

Magnetic Disk Used the most for permanent

storage in computers In principal, stores data pretty

much the same way as tapes Magnetic coating covers the disk Takes magnetic charge to

represent data Divided into tracks and sectors

Tracks are concentric circles on the disk

Sectors divide the disk into pie-shaped areas

Data fills all track within one sector

All tracks can store the same number of bits!!! more compact towards

the center (higher density)

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R/W Head

R/W head can move to any position (sector, track) on the disk random access

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Overview of Computer Hardware

Comes in two forms: Portable

Floppy disks Because they are flexible (easily bent) 3.5’’ 1.44 MB

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Calculations

Information Given : A magnetic disk is labeled M Able to write on 1 side. 40 sectors 60 tracks 1 cluster = 2 sector track I sector-track=512 byte

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Calculate

The number of sector-track on one side? 40 x 60 = 2400 sector-track The number of sector-track on both sides? 2400 sector-track because the other side =

0 How much can be stored on one side? 2400 x 512 byte = 1228800 bytes How much can be stored on both sides? 1228800 bytes

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Calculate

How many cluster on one side? 2400/2= 1200 clusters How many cluster on entire disk? 1200 clusters What is the total track in the entire

disk? 60 tracks

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Exercise in class

Information Given : A magnetic disk is labeled J Able to write on 2 sides. 80 sectors 90 tracks 1 cluster = 2 sector track I sector-track=512 byte

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Calculate :

The number of sector-track on one side? The number of sector-track on both sides? How much can be stored on one side? How much can be stored on both sides? How many cluster on one side? How many cluster on entire disk? What is the total track in the entire disk?

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Overview of Computer Hardware

Fixed Hard disks Single (PCs) or multiple (~

10 to 12) Multiple GBs per disk Diskettes have 135 tracks

per inch and 18 tracks HDs have 1000s of tracks

per inch and 64 tracks R/W does not touch the

surface but floats right above it Rotate 100 times faster than diskettes

They are sealed so that no dirt comes between R/W head and disk (corrupts data)

Disk Pack

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Overview of Computer Hardware

Compact Disks (CDs) Optical disk Data stored like magnetic disks (series of dots on tracks)

Now we BURN the dots (rather than magnetic charges) as pits on the surface

A laser detects those pits as 0s Data spans a track of the disk (not sectors) Pits gives the advantage of more density of storage

600 MB to 10 GB Most CDs are Read-only (because of the burning) Some optical drives do allow for re-burning of surface

after smoothing out the pits

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Cutaway View of a Multi-Platter Hard Disk Drive

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Simplified View of Disk Track and Sector Organization

An integral number of sectors are recorded around a track

A sector is the unit of data transfer to or from the disk

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Simplified View of Individual Bits Encoded on a Disk Track

Inside tracks are shorter & thus have higher densities or fewer words

All sectors contain the same number of bytes Inner portions of a

platter may have fewer sectors per track

Small areas of the disk are magnetized in different directions

• Change in magnetization direction is what is detected on read

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Photo of Disk Head, Arm, Actuator

ActuatorArm

Head

Platters

{Spindle

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Disk Device Terminology

Several platters, with information recorded magnetically on both surfaces (usually)

Actuator moves head (end of arm,1/surface) over track (“seek”), select surface, wait for sector rotate under head, then read or write “Cylinder”: all tracks under heads

Bits recorded in tracks, which in turn divided into sectors (e.g., 512 Bytes)

Platter

OuterTrack

InnerTrackSector

Actuator

HeadArm

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DVD Replacing CD-ROM Holds much larger amount of

information (such as movie) Also does not work on library

computers

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Zip Disk

Similar to floppy Thicker form Holds more information Available on some library computers Also becoming obsolete

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Flash Drive

Most recent widely used storage system

Very portable, often worn like jewelry 128-512 Megabytes most common

sizes

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Classes for beginners

No particular order in this group Free! Can take more than once

Basic Skills Internet Level 1 MS Word Level 1

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Time to practice a bit

Advance twice to end slide show If time allows you will practice a bit to

see what it is like to take our classes

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The End

Zainudin Johari

B Sc (Hons ) Computer Science, UPM M Sc Information Systems, UPM