MELJUN Computer System Foundation

8/14/2019 MELJUN Computer System Foundation

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ComputerSystems

MELJUN CORTES,BSCS,ACS



What is this unit about?

• Languages and translators

• Operating Systems

• Low-level machine

• Hardware

– Backing storage

– Input devices

– Output devices

0 1 0 1 0 1 0 1 0

1 0 1 1 1 1 1 1 1

1 1

I / O

F o r c o u nt e r = 1 t o 3 0

P r i nt “ E nt e r ”



01010101100001110101011010101101010101011101010010100101010101010101011011111111010010110101011010101010111010100101001010101011011111111010010110101011010101010111010100101001010101101101111111101001011010101101010101011101010010100101010110110111111110100101101010110101010101110101001010010101011011011111111010010110101011010101010111010100101001010101101101111111

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1011101010010100101010110100101001010101010101

Machine Code



What does this say?

Je ne parle pas Français ainsi je ne peux pas comprendrececi ! !

I don't speak French so I can't understand this!!

=



Languages and

Translators• Computers only understand 1s and 0s

• This is called machine code.

• It is very hard for people to read andunderstand

Instead of trying to write machinecode, we use high level languages toprogram.



High-level languages

What does a high-level language looklike?

PRINT “PLEASE ENTER YOUR AGE”

INPUT AGE

PRINT

“YOU ARE

“: AGE

Short Instructions like sentences

Made up of English words



High-level languages• High-level languages are portable.

• They can be translated into manydifferent versions of machine code

• Machine code is not portable as it onlyworks for a certain processor

PRINT “PLEASE ENTER YOUR AGE”

INPUT AGE

PRINT “YOU ARE “: AGE

Translator

0 1 0 1 0

1 1 00 1 0 1 0 1 1 0 0

1 0 1 0 1 1 0

http://images.google.co.uk/imgres?imgurl=http://www.orange-mobile-phone-deals.co.uk/sony_ericsson_t610_big.gif&imgrefurl=http://www.orange-mobile-phone-deals.co.uk/sony_ericsson_t610_mobile_phone_deal.html&h=238&w=155&sz=10&tbnid=SlN04UssEf4J:&tbnh=104&tbnw=67

http://images.google.co.uk/imgres?imgurl=http://www.groton.k12.ct.us/WWW/cc/COMPUTER.GIF&imgrefurl=http://www.groton.k12.ct.us/WWW/cc/&h=426&w=469&sz=13&tbnid=JAwVjI6ZFTsJ:&tbnh=113&tbnw=125&hl=en&start=3&prev=/images%3Fq%3Dcomputer%26svnum%3D10%26hl%3Den%26lr

http://images.google.co.uk/imgres?imgurl=http://www.mine-safety.mtu.edu/clipart/other/computer.gif&imgrefurl=http://www.mine-safety.mtu.edu/clipart/other/other.htm&h=526&w=462&sz=36&tbnid=iOhLcm9UM3gJ:&tbnh=129&tbnw=113&hl=en&start=2&prev=/images%3Fq%3Dcompute





SummaryComputers only understand 1s and 0s, which we callmachine code.

Humans write programs in high level languagesbecause they are like English, and can be translatedinto machine code.

High level languages can be portable which means

they can be translated into different kinds of machinecode.



Operating Systems

An operating system controls all thetasks the computer does for you

Reads in data from keyboardand mouse

Sends text and

graphics to thescreen

Sends datato yourprinter

• Loads data into thememory from the HardDisk

• Saves your files to disk



Examples of OperatingSystems

• Microsoft Windows

• Apple Mac OS X

• Linux

But NOT things like:

• Microsoft Word

• Games• Internet Explorer

– These are programs that run on theOperating System



Types of File

There are two different types of file:

Program files, which are files full of instructions that the system runs.Microsoft Word is a program file.

Data files, which are used by programs.A Microsoft Word document (like a letteryou wrote and saved) is a data file.



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CC

umanuman

omputeromputer

nterfacenterface



Human Computer Interface

• The Operating System provides theHCI for the user

• User uses mouse to click icons• Operating System translates into

instructions

– What was clicked?– What should be done now (load file,

save file, load program)?



Types of Operating System

Interactive System– Computer reacts to user requests

immediately and processes the data

– Example: Internet ticket booking (Travel,

Concert)

What would happen if the system

wasn’t interactive?

1. User clicks on link to buy ticket

2. System checks immediately if there is

a ticket available

3. Ticket is booked for the user



Types of Operating System

Real Time System– Real time systems react even faster thaninteractive systems

– Designed to always process the rightamount of information in time

– This means the Real Time system isinstant every time

Used in spaceship control systems,

nuclear reactors…..

Where else would Real Time

Systems be used instead of Interactive S stems?



Summary

Operating systems control the tasks the computer does for theuser. This includes loading data into memory, reading data fromthey keyboard and mouse, saving files and sending text andgraphics to the screen or printer.

There are two types of file - program files (such as Microsoft

Word) and data files, that are used by program files (such as aletter your wrote in Microsoft Word)

We interact with the OS through the Human Computer Interface(HCI). The OS translates the keyboard and mouse presses into

instructions and performs actions such as loading and savingfiles.

Interactive operating systems are used when users needimmediate feedback. Real-time operating systems are usedwhen systems always need instant results (such as a control

system on a plane).



Check your understanding

What kind of system would you use forthe following (choose frombackground, interactive and real-time):

• Flight booking web site

• Controlling a robot?

• On a home computer?• Running a nuclear reactor

Int er act iv eReal-

T imeInt er act iv e

Real-t ime



More Checking!

• What jobs does the Operating System do?• Give an example of an Operating System?

• What are the 2 types of file?

• What does the HCI do?

• When would Interactive Processing be used?• When would Real-Time Processing be used?



Filing Systems

• It is very wise to organise yourfiles!

• Lots of files in the one place =hard to organise

• Group them in directories



Filing System

The OperatingSystem sorts our

data usingdirectories(often called

folders) and files.



Low Level Machine

• We now know about Operating Systems, High LevelLanguages, and how we access data.

• What’s next?

Now we are going right inside thecomputer to look at how the CPU and

memory works



The two most important parts of the inside of the computer arethe CPU and memory.

The CPU (Central Processing Unit) is the “brain” of the computerwhere the computer works things out.

The memory is where the computer “remembers” things for theCPU.



The Computer’s Memory

Computers use main memory and backing storage to store data.

Main memory is the fast memory inside a computer

that stores data the CPU is currently using

Backing store is the bigger but slower memory thatstores files and programs for the computer

Backing store comes in two types – magnetic andoptical.

Magnetic – Hard Disk and Floppy disk

Optical – CDROM and DVD



Main memory

• Inside the computer there is main memory

• Main memory is made up of memory chips

• There are two kinds of main memory:

RAM – Random Access Memory

ROM – Read Only Memory



Random Access Memory

• RAM is where the computer stores data thatis it currently using. This includes:

– Data from the keyboard as you type

– Data from open files and programs you are

using

• When you turn off your computer, all the datain RAM will be lost.

• This is why you must always save files tobacking store before turning off a computer!

http://images.google.co.uk/imgres?imgurl=http://www.build-your-own-computers.com/images/how-to-buy-computer-memory-1.jpg&imgrefurl=http://www.build-your-own-computers.com/how-to-buy-computer-memory.html&h=211&w=298&sz=9&tbnid=A00325g5J5EJ:&tbnh=78&tbnw=111&hl=






Read Only Memory

• ROM is READ ONLY – you can’t change it

• It is written in the factory when the computer is made

• The computer can read the data in the ROM straightaway when the computer is switched on

– This is why parts of the OS are sometimes stored onROM

• It isn’t wiped when the computer is switched off

• A good way to remember the differencebetween RAM and ROM is to think that RAM is

like a notebook and ROM is like a textbook.• With RAM you write in what you need toremember

• With ROM it is already there and you don’tchange it!




How to measure memory

• We said before that everything in a computer iseither a 1 or a 0

• This is because computers use binary numbers

• The size of memory is usually given in megabytesor gigabytes, but what does that mean?

Bit Binary digit: a 1 or 0

Byte 8 bits, e.g. 01101100

Kilobyte 1024 bytes

Megabytes 1024 KilobytesGigabyte 1024 Megabytes

Terabyte 1024 Gigabytes



Memory size

Bit Binary digit: a 1 or 0

Byte 8 bits, e.g. 01101100

Kilobyte 1024 bytes

Megabytes 1024 Kilobytes

Gigabyte 1024 Megabytes

Terabyte 1024 Gigabytes

So an iPod with 60GB of storage spacehas:

60 x 1024 x 1024 x 1024 x 8

= 515,396,075,520 bits!

(over 515 billion bits…)



The Processor

The processor is the brains of the computerA processor takes data in, processes it and then

outputs the data to screen or printer.

Input Process Output

keyboard

mouse

calculationPrint out

Display onscreen



Remember:

Input

Process

OutputSome real world examples of IPO…..



Check your

understanding…• Give a real life example of IPO

• Give a computer example of IPO

• Explain why you can not store datain ROM

• What happens to RAM when the

computer is switched off? Whyshould this be ok?



B

I

N

A

R

Y



Binary

• We count in “decimal”

• We have 10 fingers, so it makes sense

that we group by 10s I.e. 1, 10, 100,1000, 10 000 etc

• Computers count in binary

• They use different columns and groupby twos I.e. 1, 2, 4, 8, 16, 32, 64, 128



Numbers

We count to 10:

1,2,3,4,5,6,7,8,9,10

A computer would do this in binary:

1,10,11,100,101,110,111,1000,1001,1010!

Binary numbers have a power of 2, and

decimal numbers (that we count with)have a power of 10. Let’s go back intime……



1000 100 10 1

128 64 32 16 8 4 2 1

6 5

1 1

1 1 5

1 1 1 1 1

0

0

0 0 0 0 0

0 0

For example:



Binary Revision Questions

• What is binary for:

48, 20, 128, 7 ?• What is the decimal for:

00001000, 00001000,

00011000, 00000101 ?





Binary recap

• 65

• 100

• 255

• 129

128 64 32 16 8 4 2 1

01000001

01100100

11111111

10000001



Storing Text and Graphics

• If computers can only work withbinary numbers, how do they store

words and pictures etc?



Storing Text

• Since computers only use binary, they

have a binary code for each character• This code is called ASCII– American Standard Code for Information

Interchange

Binary Decimal Character

1000001 65 A

1000010 66 B

1000011 67 C

1000100 68 D

1000101 69 E1000110 70 F

Let’s try some ASCII conversion….



ASCII Table

http://www.ascii.cl/htmlcodes.htm



ASCII TABLE

65 A

66 B

67 C

68 D

69 E70 F

71 G

72 H

73 I

74 J75 K

76 L

77 M

78 N

79 O

80 P

81 Q

82 R

83 S

84 T

85 U

86 V

87 W

88 X

89 Y

90 Z



The size of a text file

Hello

The eagle has landed!

How many bytes would these files take up?

• Text is stored in the computer using ASCII codes

• Each character’s ASCII code is8-bits, i.e. 1 byte in size

• So, we can work out the storagerequirements of text files

5

21





Storing Graphics

• In black and white graphics, thegrid of pixels can be represented

by binary numbers• 1 stands for a black square, 0

stands for a clear square.

• Each pixel takes up 1-bit to store.

1 0 0 1 1 0 0 1Th id i 8 8 i l



1 0 0 1 1 0 0 1

0 1 0 1 1 0 1 0

0 0 1 1 1 1 0 0

0 0 0 1 1 0 0 0

1 0 0 1 1 0 0 0

1 1 1 1 1 0 0 0

0 0 0 0 1 1 1 0

0 0 0 0 0 0 1 0

How many bits do

you think it will taketo store this graphic?

The grid is 8 x 8 pixels,so it will take 64 bits tostore.

64 bits is 8 bytes.



Colour

Graphics• To store colour graphics, we need to

assign each colour a different numbere.g. red = 1, blue = 2 etc.

• These colour codes are stored in binary

• The larger the binary number, the more

colours we can have. How many do weneed?

• 32-bit graphics are normal (4.3 billiondifferent colours)



Systems task 9

• 10 minutes on Systems Task 9,page 25

• If finished, go onto KnowledgeCheck 5



Summary

• Computers store text and graphics in binary.

• They use a code called ASCII (American Standard Codefor Information Interchange)

• Each character has a code in ASCII• Black and white graphics are stored by using 1 bit for

each pixel (1 for black, 0 for white).

• We can work out the size of these graphics bymultiplying the width of the graphic by the height.

• Colour graphics use more bits for each pixel dependingon how many colours are needed.



Hardware

• We’ve covered how the CPU works,and what the Operating Systemsoftware does

• Now let us look at hardware for thecomputer



Microprocessor

The chip is made of layers of silicon crystalwavers on which very small electronic

components are installed.



Backing Storage

Backing storage memory is used to store files when thecomputer is switched off, and are usually removable.

There are two types of backing storage, Optical andMagnetic. We’ll look at magnetic first.





Tape Drive

Tape drives take large plastic tapes which store data in binaryusing magnetic ‘spots’ to encode the data

They have a large capacity, and fast data transfer rates

Tapes wear over time so need to be stored in suitableenvironment and are suited to medium and short termstorage

DAT tapes can hold up to 200 Gigabytes so are used forbackup





Floppy Disks

• Floppy Disks are made from circular plastic plates coated iniron oxide (which is a magnetic chemical).

• Data is stored on the surface as patterns of magnetic spots.

• Floppies are small and compact

• They store up to 1.44Mb of data (about 1/3 of an MP3 file)

• They can be damaged easily by dust, dampness,electro/magnetic pulses

Hard Drive



Hard Drive

Hard Drive



Hard Drive

Hard drives store data by writing

magnetic patterns onto metaldisks.

The surfaces are divided up intosectors and tracks which allows

each part to be accessed directly.

• The disk is in a sealed box to prevent dust damage.• The read/write head is just above the surface of thedisk

• The disk spins between 7,000 and 10,000 rpm• They hold gigabytes of data (most recently up to750GB in size)



Optical Backing Storage

Optical backing storage uses laseroptics to read and write data.

Data is stored in binary by usinglasers to burn microscopic marks onthe disk surface.

Data is read by reflecting light off thesurface to read the microscopicmarks.







DVD-ROMDVD-ROM

• Works in the same way as CD-ROM• Stores more data because it uses a narrower laser

beam to read and write to disk

• Ordinary DVDs hold 4.7 Gigabytes

• Double-sided, multilayered DVDs store up to 17GB• Enough space for large files such as movies

• Works in the same way as CD-ROM• Stores more data because it uses a narrower laser

beam to read and write to disk

• Ordinary DVDs hold 4.7 Gigabytes

• Double-sided, multilayered DVDs store up to 17GB• Enough space for large files such as movies



CD-RCD-R

• Stands for Compact Disk Recordable

• Uses a layer of dye which laser changes tostore data

• CD-Rs are WORM - Write Once Read Many

– Once files are written on, they can’t be deleted orchanged

– CD-Rs are read-only after they are written

• Stands for Compact Disk Recordable

• Uses a layer of dye which laser changes tostore data

• CD-Rs are WORM - Write Once Read Many

– Once files are written on, they can’t be deleted orchanged

– CD-Rs are read-only after they are written



CD-RWCD-RW

• Stands for Compact Disk Re-writable

• Unlike CD-R, these can be rewritten

• This is because they use the laser to change the

reflective properties of microscopic marks

• CD-ROMS, CD-Rs and CD-RWs are used for:– backing up large files

– Storing large multimedia presentations

– Storing large programs, like games

• CD-ROMS, CD-Rs and CD-RWs are slower than hard disks

• But they are removable!

• Stands for Compact Disk Re-writable

• Unlike CD-R, these can be rewritten

• This is because they use the laser to change the

reflective properties of microscopic marks

• CD-ROMS, CD-Rs and CD-RWs are used for:– backing up large files

– Storing large multimedia presentations

– Storing large programs, like games

• CD-ROMS, CD-Rs and CD-RWs are slower than hard disks

• But they are removable!



DVD-R and DVD-

RW

DVD-R and DVD-

RW

• Works in the same way as CD-R and CD-RW• Stores more data because of narrower laser

• Can store up to 4.7GB

• Works in the same way as CD-R and CD-RW• Stores more data because of narrower laser

• Can store up to 4.7GB





USB Flashdrive

USB Flashdrive

• USB Flash drives are rewritable memory chips• Store data just like a disk

• Used as backup and plugs into USB ports on acomputer

• Very small and portable• Sizes from 64MB to 2 Gigabytes

• USB Flash drives are rewritable memory chips• Store data just like a disk

• Used as backup and plugs into USB ports on acomputer

• Very small and portable• Sizes from 64MB to 2 Gigabytes



Input Devices

Input devices are pieces of hardwarethat let you control a computer bysending data to the computer fromyour device.



MouseMouse

A mouse lets youcontrol the pointeron screen, and clickto select icons.

Mice usually have 2buttons andsometimes a scroll

wheel.

A mouse lets youcontrol the pointeron screen, and clickto select icons.

Mice usually have 2buttons andsometimes a scroll

wheel.



TrackballTrackball

A trackball is similarto a mouse exceptthe ball is on top.

The trackball doesnot move around the

desk like a mouse.

They are usefulwhen a user does

not have desk spaceto move a mouse,and for people whofind it hard to usetheir arms to moveob ects around.

A trackball is similarto a mouse exceptthe ball is on top.

The trackball doesnot move around the

desk like a mouse.

They are usefulwhen a user does

not have desk spaceto move a mouse,and for people whofind it hard to usetheir arms to moveob ects around.





Graphics

Tablet

A flat plastic panel with electronic sensors belowthe surface detect the movements of a pointingdevice.

Very accurate – used by graphic artists / designers /Computer Aided Design (CAD)

Touch Sensitive Screen



Touch Sensitive Screen

Simple to operate

Useful for public informationsystems

Tiring to use after a while

Not precise

Keyboard



Keyboard

Input text and numbers

Function keys

QUERTY layout

Very common, nearly every computer

has one



Scanner

Input drawing, photographs frompaper.

Light beam passes over page and asensor detects the reflection

Optical Character Recognition (OCR)

software can recognise writing

Di it l C



Digital Cameras

Di it l C



Digital Cameras

Captures light coming through the lensand stores a digital image

Allows instant review of picture takenDelete photos you don’t like

Takes a memory card – can be various

capacities.

Ch i



Choosing a camera

Look at the accuracy (resolution) –measured in Megapixels. 5 Mpx isenough

Does it have a zoom lens? Digital zoomis worthless because it produces poorpictures

What capacity is the memory card?



Digital Video cameras

Same principle as still digitalcameras

Need a large storage capacity –

video takes up a lot of space (15frames per second)

Some have a small LCD screen

to view your videoFeatures: zoom, focus, lighting,infrared recording, onboardediting



Laser Printer



Laser Printer

Uses a laser beam to copy image of a page onto light-sensitive drum

Ink (toner) attracted to the drum

then transferred to paper

Laser printers are fast

The output is high quality

They are expensive to buy butrelatively cheap to maintain.

Sprays ink onto the paper

http://images.google.co.uk/imgres?imgurl=http://www.atlex.com/hp/5-images/printer-images/designjet_30.jpg&imgrefurl=http://www.atlex.com/hp/1-printers/hp-designjet/30.htm&h=736&w=1200&sz=296&hl=en&start=58&tbnid=2C_iwD63q7-s5M:&tbnh=92&tbnw=150&prev=/images%3Fq%3Dinkjet%2Bprinter%26start%3D40%26imgsz%3Dxxlarge%26ndsp%3D20%26svnum%3D10%26hl%3Den%26lr%3D%26sa%3DN



Inkjet Printer

Sprays ink onto the paper

Printout quality is high

Cheap to buy, can beexpensive to maintain(expensive ink)

Slower than Laser Printer

http://www.mirusinnovations.com/assetsftp/615L34.jpg

http://images.google.co.uk/imgres?imgurl=http://www.atlex.com/hp/5-images/printer-images/designjet_30.jpg&imgrefurl=http://www.atlex.com/hp/1-printers/hp-designjet/30.htm&h=736&w=1200&sz=296&hl=en&start=58&tbnid=2C_iwD63q7-s5M:&tbnh=92&tbnw=150&prev=/images%3Fq%3Dinkjet%2Bprinter%26start%3D40%26imgsz%3Dxxlarge%26ndsp%3D20%26svnum%3D10%26hl%3Den%26lr%3D%26sa%3DN

http://images.google.co.uk/imgres?imgurl=http://www.techflare.com.au/images/articles/reviews/15-1.jpg&imgrefurl=http://www.techflare.com.au/viewreview.asp%3FarticleID%3D15&h=596&w=1000&sz=139&hl=en&start=21&tbnid=BzuJY9JwKLN3mM:&tbnh=89&tbnw=149&prev=/images%3Fq%3Dinkjet%2Bprinter%26start%3D20%26imgsz%3Dxxlarge%26ndsp%3D20%26svnum%3D10%26hl%3Den%26lr%3D%26sa%3DN

http://www.mirusinnovations.com/assetsftp/615L34.jpg



Monitor



Monitor

Screen used to display

computer output

Different monitors havedifferent resolutions

The higher theresolution, the moredetailed the picture will

beHigh resolution neededfor CAD and art work



LCD / TFT Displays

LCD = Liquid Crystal Display

These screens have the followingadvantages:

Flat, light, needing little power, can berun from a laptop battery

The one disadvantage is that sometimesthey are not bright enough and cancause eye strain



LCD / TFT Displays

TFT = Thin Film Transistor

Same advantages as LCD.Uses a tiny transistor to form each pixel

Can update the image very quickly,

allowing it to handle complex graphicsand animation which LCD displayscannot

Computer



ComputerSpeakers

Produce sound from the computer

Allow you to do multimedia presentations,

video-conferencing, games, music etcComputer speaker systems vary in qualityand number of speakers depending onoutput wattage (RMS) or surround sound





Desktop VS Laptop

• Desktop computers stay in the sameplace. Laptop computers are portable

• Because of this, the components used

need to be light and consume lesspower (run off battery)

• This means that a laptop with the samespecification (CPU speed, RAM) will

cost more than a same spec desktop.





Palmtop Computer

• Is about the size of your hand

• Small keyboard or a stylus withhandwriting recognition

• Stores data on a memory card• Useful for ultra-portable computing

on the move

• Store contacts, calendar, editing

documents, email etc



Mainframe computer

• Large and powerful

• Lots of processing power

(multiple CPUs) and RAM• Many users connectedusing terminals

• Used by banks and other

large businesses toprocess and store data

http://upload.wikimedia.org/wikipedia/en/8/8a/Z890.jpg



Multimedia Systems

• Multimedia systems integrate sound,animation, video and graphics

• Most modern computers have these

capabilities

• Interactive learning,

information systems,multimedia web pages,games



Multimedia systems

• A fast CPU and lots of RAM and storage

• Quality TFT display

• Scanner

• Digital camera (video)

• Surround soundspeakers

• Data projector

A good system for viewing and creatingmultimedia might include:

MELJUN Computer System Foundation

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