A computer is an information processing machine'

1
What is a Computer?

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

Im ONLY a machine!
2
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

3
Data and Information

• Data has no meaning
• Data is made up of symbols e.g.
• 871652 H789 IOS 76.91
• Information has a meaning
• We understand what a piece of information is
  about e.g
• Telephone Number 871652
• Car License Plate H789 IOS

4
IPO - Input, Process, Output
INPUT
PROCESS
OUTPUT
Data is INPUT into the computer system It is then
PROCESSED to produce useful Information as OUTPUT.
5
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

6
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.

Device
Media
7
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).

8
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.

9
Input Devices

• Mouse
• 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.
• Keyboard
• Similar to a typewriter, contains the letters for
  typing text, and keys that give the computer its
  commands.
• Touch Sensitive Screen
• A Touch Sensitive Screen is a pointing device
  that enables the user to interact with the
  computer by touching the screen.

10
Input Devices

• Trackball
• A 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.
• Trackpad
• A 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.

11
Input Devices

• Graphics Tablet
• A 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.
• Joystick
• Joystick 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.

12
Output Devices

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

13
Output Devices

• Printers
• Laser 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).
14
Output Devices

• Printers
• Inkjet 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.

15
Output devices
Comparison of Laser with Inkjet

• Laser printer
• Expensive to buy
• High quality output
• Very quick to print a page
• Relatively low cost of toner
• Prints quietly
• Colour models expensive and most costly to run

• Inkjet printer
• Cheap to buy
• Good quality output (but not as good as laser)
• Slow to print a page
• Relatively high cost of new ink cartridges
• Quiet, but noisier than laser
• Relatively cheap colour printing when compared to
  laser colour printing.

16
Backing Storage Devices

• Magnetic Tape
• A 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.

17
Backing Storage Devices

• Floppy disk
• The 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 disc
• A 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.

18
Using disks and making backups
Write Protect Tab
Disc Label

• 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 -
• Lost
• Corrupted (i.e. made unreadable)
• Damaged
• Stolen
• You should always make a backup of important
  files.
• And dont keep the backup in the same place as
  the original copy!

19
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 Icon
• Left 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.

20
Copying to a Disc (Windows)

• Locate the files you want to copy.
• Select the files to be copied
• Left 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.

21
Backing Storage Devices

• CD-ROM
• A 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-ROM
• Digital 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

22
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

23
A typical Local Area Network

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

Printer
Work Station
Fileserver
Network Cable
24
Types of Computers
Smallest

• 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.

Biggest
25
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.

26
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.
27
Computer System - Block Diagram

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

Data Flow
28
What is the CPU

• CPU - Central Processing Unit
• It is the combination of the Processor and
  Memory.
• There are TWO types of memory in the CPU, RAM and
  ROM.

Central Processing Unit
ROM
RAM
PROCESSOR
Data Flow
29
RAM and ROM

• RAM is Random Access Memory
• It 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 Memory
• Data 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).

30
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 dont need to understand binary (thats
  Maths) but you do need to know that it is how
  most numbers are stored in the computer.

31
Storing Graphics

• Black 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.

32
Storing Text

• Text 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 51
• ASCII (American Standard Code for Information
  Interchange)
• One ASCII code is one byte long (eight bits).

33
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
34
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.

35
Types of Computer

• Mainframe Computer
• A 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.

36
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 software
• Program - 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)

37
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 CODE
• Machine code is DIFFERENT for each type of
  processor Apple Mac computers use a different
  processor and therefore a different machine code
  from PCs.

38
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 CODE
• Machine code looks like this
• 00100111,01110100,10010001
• NOT very easy to understand.
• Thats why High Level Languages have been
  produced...

39
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...

40
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.

41
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.

42
Types of High Level Language

• General purpose
• General 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 Purpose
• Special 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.

43
OS - Different modes of processing

• There are several different modes of processing.
• Interactive
• Accepting 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 Time
• Real-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.

44
More Input Devices

• Scanner
• A 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 Camera
• A 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.

45
More Input Devices

• Digital Video Camera
• A 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.
• Webcam
• a digital camera designed to take digital
  photographs and/or video and transmit them over
  the internet