UNIT 2 Computer Architecture
| b the capacity (size) of the memory (MB -megabytes) c the capacity (size) of the magnetic storage devicese.g. hard disk, floppy disk (MB -megabytes, GB - gigabytes) d the speed of the optical storage devicese.g. CD-ROM, DVD (given as a multiple of the speed of the first devices produced e.g. 24x = 24 times, 12x = 12 times) e the display monitor size (measured in inches diagonally across the screen surface) f the monitor image quality (resolution)given by the number of pixels(picture elements) that are used across and down the screen e.g. 800 x 600, or by the graphics standard used e.g. VGA(video graphics array), SVGA(super video graphics array) g the graphics card memory size (MB -megabytes) h the speed of the modem (measured in kbps- kilobits per second) Two different number systems are used in computer specifications: a The decimal system,which consists of ten digits from 0 to 9, is used for measuring speed. | b The binary system,which only has two digits (1 and 0), is used for measuring capacity. The following prefixes are also used in measurements: | ||
| Decimal system | Binary system 11 | ||
| kilo | 103 = 1 thousand | 210= 1,024 | |
| mega | 106=1 million | 220= 1,048,576 | |
| giga | 109 = 1 thousand million | 230 = 1,073,741,824 | | | |
| e.g. 1.7 GHz = one point seven thousand million cycles per second 256 MB = 256 x220 bytes = approximately two hundred and fifty six million bytes Communication is provided between applications programs(wordprocessors, drawing programs, etc.) and the computer hardware(the physical components of a computer system) by a set of programs collectively known as the operating systeme.g. Microsoft Windows, MacOS. |
UNIT3
Computer Applications
INTRODUCTION
As computer systems become more intelligent, they are used in a wider variety of work situations where previously it was necessary to employ people. Hospitals can increasingly use computers where highly trained people were required to deal with life-threatening situations. Computers can also be used in airports where highly trained experts were previously required to ensure safety and the police can make more use of computers to detect and investigate increasingly sophisticated crimes.
One of the uses considered in this unit is police speed trapsused to catch drivers that are breaking the official speed limit. In earlier systems, radarequipment was used to bounce radio waves off the moving car. A small processor, known as a microprocessor,calculated the speed of the car from the changes in the radio waves and triggered an ordinary camera with a flashgun to take a photograph of the car if it was speeding. The details were stored on a smart card(a plastic card with a built-in computer system that can store large amounts of data). When the smart card was taken back to the police station, the driver's details were obtained from the DVLC(Driver and Vehicle Licensing Centre) databasei.e. the central computerised records of all licensed drivers and vehicles.
Newer systems prevent 'surfing*i.e. where the driver only slows down as they pass through the speed trap, by using two computerised units with digital cameras placed at a fixed distance apart. Each unit records the time that a vehicle passes it, as well as photographing and identifying the car licence number using OCR software(optical character recognition software that changes picture images of letters and numbers into digital form for use by a computer system).
The computer then uses the difference in recorded times to calculate the speed of the vehicle. The registration numbers of vehicles exceeding the speed limit are immediately downloaded(copied from the computer to a server computer) to the computer at police headquarters where each vehicle is matched with the DVLC database. Standard letters are then printed off addressed to the vehicle owners using mailmerge(a wordprocessing feature that produces a separate standard letter containing details obtained from each record in a database).
There are many ways in which computer systems can be used in large supermarkets, I particularly for financial calculations and in stock control using EPOS tills(electronic point of sale cash tills). Each item on a supermarket shelf has a barcode labelwith a barcode(a standard set of vertical bars of varying thickness used to identify products) printed on it. The barcode number system giving standard price and item code numbers used throughout Europe is known as EAN(European Article Number). The barcodes are read by scanner devices called barcode readersthat are attached to the EPOS tills. When a checkout operator moves the barcode label across the scanner, the label is scanned and the barcode number for that item is read. The scanner signals are converted to a digitalform (where the changing signal is either off or on) and sent to the supermarket branch computer. The branch computer checks the digital EAN code against a computer database(a type of applications program used for storing information so that it can be easily searched and sorted) that holds a record of each type of item. In this way the item and the price of the item can be identified and the sale of the product can be recorded by the computer. The item and the price are shown
22 UNIT 3Computer Applications
| on the EPOS till display and printed on a paper receipt. Computers are also used to provide cash to users and to process bank cards such as | Visa cards using an ATM (automatic teller machine - the type of machine used by banks for enabling customers to withdraw money from their bank accounts). |
OBJECTIVES
UNIT 4
Peripherals
INTRODUCTION
EPOS(electronic point of sale) tillsused in supermarkets form part of a computer system with various input and output peripheraldevices attached to the till, including: electronic scalesfor weighing produce, barcode readerfor looking up prices using barcodes, swipe card readerfor reading bank cards, numeric keypadfor inputting prices manually, LCD(liquid crystal display) screen for outputting purchase details.
Digital camerasare gradually being developed that are as good as conventional cameras. They have various electronic devices inside, including:
a LCD(Liquid Crystal Display) screen used as a view-finder and for viewing the pictures after they have been taken.
b CCD(Charge-Coupled Device) consisting of thousands of photo-transistors(light-sensitive transistors - a transistor is an electronic switch). It creates the pictures as a set of dots or pixels(picture elements).
: Memory cards e.g. flash cards - solid state memory(electronic integrated circuits, i.e. chips, used for storing the pictures).
There is no delay in getting pictures from digital cameras because there is no film requiring chemical processing. They can be attached to a computer to directly transfer pictures for editing using special software and unwanted pictures can be deleted. However, they cost more than conventional cameras and the quality is not quite as good. You also need to buy rechargeable batteries and a photo-quality colour printer with high printing costs for paper, ink, etc. Two important features when buying a digital camera are:
a picture quality or resolution.The resolution of a camera is measured in pixels and given as two numbers, indicating how many pixels there are across the image and how many going down the image e.g. 1280 by 960 (or 1280x960).
b the number of pictures the camera can store. The higher the resolution, i.e. the more pixels, the more memory is required to store the pictures. Data can be compressed to allow more pictures to be stored.
Storage devicesare used to store data and programs that are not being used by the processor. They usually consist of:
a storage mediain the form of a circular disk or a tape where the data is stored
b a disk or tape drivethat moves the media past a read/write headthat reads the data from and writes data to the storage media.
| Types of storage devices include: | |
| magnetic | floppy disks(diskettes) and |
| devices(that | magnetic tapemade of a |
| use magnetism) | magnetic coated flexible |
| plastic; hard disksmade of ] | |
| magnetic coated aluminium | |
| disks. | |
| optical devices | CD-ROM- compact disk |
| 1 (that use laser | read only |
| light) | memory |
| CD-R- recordable | |
| compact disk | |
| CD-RW- re-writable | |
| compact disk | |
| DVD-ROM- digital versatile | |
| disk read only | |
| memory | |
| DVD-RAM- digital versatile | |
| disk random | |
| access memory |
26 UNIT 4Peripherals
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| magneto-optical devices(that use a combination of magnetism and laser light)______ |
CD-MO- magneto optical compact disk
Read only mediaenable the user to both read data from and write data to the media. Read and write mediacan only be used for reading data i.e. the stored data cannot be changed in any way.
Removable storageenables the user to change the media and transfer it to another computer.
Fixed storagedoes not allow the media to be changed or transferred to another computer.
Other factors that vary between storage
devices include:
a the speed at which the drive moves the media past the read/write head and reads or writes data to the storage media
b the capacity of the media i.e. how much data can be stored on each disk or tape
c the cost of the drive and the media.
There are various types of printersfor out-putting text and graphics to paper.
Some types of printers are mono(print in black and white only) and others can print in colour. The speed, quality and cost of printing varies between different types of printer. Some are designed for printing text and are not really suited to printing graphics.
| Data can take many forms and there is a wide variety of input, output, storage and communication peripherals. Units of measurementused in data storage include: | |
| bit | a binary digit i.e. a 1 or a 0 II |
| i byte | 8 bits = 1 character i.e. a letter, numerical digit or a punctuation mark | |
| megabyte (MB) | 1,048,576 bytes (approximately one million bytes) |
| gigabyte (GB) | 1,073,741,824 bytes (approximately one thousand million bytes) |
| terabit | 1,099,511,627,776 bits (approximately one thousand gigabits) |
| micron | one millionth of a metre |
| angstrom | the approximate radius of an atom J |
UNIT6
Operating Systems
| INTRODUCTION ^g^g^^^g | a command). The screen is usually blank except for a symbol (e.g. $) which acts as a command prompt.When the command is typed at the prompt and the Enter key is pressed, the command is processed and the output is displayed on the screen. OS commands are usually short words or abbreviations (e.g., date, logout, passwd, Is). Unixis a command driven operating system used on all sizes of computers, but mostly large multi-user, multi-tasking mainframe computers. It is available in many versions, such as Linux, Minix, HP-UX, Xenix, Venix, Ultrix, A/UX, AIX, Solaris, and PowerOpen. Other command driven operating systems mentioned in this unit include: VAX/VMS, MVS VM OS/390, NetWare, MS-DOS and PC-DOS. Some operating systems have a GUI(pronounced like 'goo-ey' - graphical user interface)that allows the user to use a mouse to click on icons on the screen or choose commands from a list of choices known as a 1 menu.Operating systems with graphical j interfaces mentioned in this unit include: MacOS, OS/2, Penpoint, Windows NT, Windows 3.x, Windows 9X and Windows 2000. |
| The OS (operating system)is the set of computer programs that allow the user to perform basic tasks like copying, moving, saving and printing files. It also provides an interfacebetween (i.e. provides communication between) applications programs(e.g. wordprocessors or spreadsheets) and the computer hardware. As a user interacts with an applications program on the screen, the applications program communicates with the operating system and the operating system communicates with the computer hardware. The work of the operating system takes place in the background and is not always obvious to the user. The most important program in an OS is the supervisor program.It remains in memory all the time that the computer is operating, and manages the OS. It loads other parts of the OS into memory when they are needed. Programs that remain in memory while the computer is in use are known as resident programs.Programs that only stay in memory while they are being used are known as nonresident programs. Some operating systems are command driven(i.e. the user runs a program by typing |
UNIT 7
Graphical User Interfaces
INTRODUCTION
A user interfaceallows a user to interact with a computer. In particular, a GUI(graphical user interface) allows the user to use a mouseto interact with the computer. Microsoft Windows(commonly referred to as Windows) is a common GUI used on PCs(IBM compatible personal computers). The main Windows background screen is called the desktop.Programs, files and folders are represented on the desktop by small images called icons.Using a mouse, the user can move a pointer (cursor)across the screen. An icon can be selectedby clickingthe left mouse button (i.e. quickly pressing and releasing the button). By holding the pointer over an icon (hovering),a text box can be made to appear that explains what the icon represents. This text box is known as a tooltip. Double-clickingthe mouse (pressing and releasing the button twice in quick succession) causes the program, file or folder represented by the icon to open in a rectangular box on the screen called a window.More than one window can be open at a time but the one with the focus is known as the active window.Windows can have a vertical scroll barand a horizontal scroll bar to allow the user to move a document up and down or across the screen respectively. A user can draga selected item from one part of the screen to another by holding down the left mouse button while moving the pointer. The user can then dropthe item at the new location by releasing the mouse button.
Commands are displayed in a menu baralong the top of the window. Clicking on a command opens a list of choices known as a menu.Clicking on a menu item sometimes opens another related menu called a submenu.Common commands include:
| Find | searches for a word, filename, or | folder name | |
| Undo | reverses the last action of the user | |
| Cut | deletes the selected text, file or folder 1 and copies it to a special area of memory called the clipboard |
| Paste | inserts the text, file or folder stored in the clipboard, at the location of the cursor , |
A bar, known as a taskbar,is displayed along the bottom of the desktop showing what programs, files and folders are currently open. At the far right of the taskbar is a special area called the system traywhere icons are displayed showing what resident programs are continuously running in the background e.g. the system clock or a sound volume control. There is a Start buttonat the far left of the taskbar. When the Start button is clicked, the Start menuopens on the screen. The user can close down the operating system by choosing the Shut Downoption on the Start Menu. A touchscreenallows the user to select icons and commands by touching the display screen with their finger instead of using a mouse. Graphical user interfaces were first introduced with the Apple Mac OS. Other GUIs with desktops, icons, pointers, windows, menus and submenus are also available.
Common iconson the Microsoft Windows desktop include:
| Microsoft Outlook |
a messaging program
| My Briefcase |
a program that allows the user to exchange files with a portable computer and to synchronise the files on each computer
UNIT7 Graphical User Interfaces 39
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| [ Network Neighbourhood or My Network Places | a feature that displays the names of other computers networked with yours |
| 1 [My Computer | a feature that lets you see the resources on your computer |
| I Internet Explorer | a browser program that allows the user to view webpages on the Internet |
| I [Recycle Bin | a feature that stores i deleted files and allows the user to restore them to their original location i.e. the equivalent to the trashcanon an Apple Mac system. |
A + sign used between the names of keyboard keys means that the user should press both keys simultaneously e.g. ALT + TAB. Keyboard keys and combination of keys mentioned in the text include:
| j Shift key | allows you to type in uppercase (capital letters) \ |
| MouseKeys feature | enables you to use the numeric keypad to i move the mouse pointer |
| ALT + TAB | allows you to switch between open programs |
| StickyKeys feature | helps disabled people to operate two keys simultaneously |
| PRINT SCREEN key | lets you copy an image of the whole screen to 1 the Clipboard |
| ALT + PRINT SCREEN | lets you copy an image i of the active window to the Clipboard |
UNIT8
Applications Programs
INTRODUCTION
Softwareis the word used to refer to programs(sets of computer instructions written in a computer language) and datathat is input, processed and output by a computer system. Applications programsare programs that allow the user to do various types of work on a computer e.g. wordprocessors, databases. A set of related applications programs is referred to as a package(or suite).Common applications programs include:
| wordprocessors | for creating and editing texts |
| spreadsheets | for performing calculations using formulas |
| databases | for storing data so that it can be easily searched and sorted |
| graphics | for drawing |
| games | for playing fast action games |
| accounts | for keeping business accounts |
| payroll | for calculating salaries |
| presentation program | for creating multimedia slide shows |
| for sending electronic mail messages | |
| PIM(personal information manager) | for keeping track of appointments, address book, task list, etc. |
| | DTP(desktop publishing program) | for creating publications to be printed by a professional printer |
| small business tools | for performing various business tasks 1 |
| website editor | for creating and editing webpages |
| image editor | for editing graphic images |
| developer tools | for writing programs to add features to existing applications and creating integrated program systems |
Some applications programs,such as wordprocessors, spreadsheets and databases, are commonly referred to as office programsbecause they are commonly used in a typical office. Office packages(or suites)such as Microsoft Officeare sets of interrelated office programs. Different versions of office suites are usually available containing different combinations of programs. Mailmergingis a useful feature found in most office suites that combines a database with a wordprocessor document to automatically produce a copy of a standard letter for each record in the database.
A variety of computer hardwareis used in the doctors* practice in this unit including:
| PC |
common name for an IBM compatible personal computer
| network |
computers connected together
| file server |
a powerful computer that stores and allows users access to data files on a network
| laser printer |
| dot-matrix printer |
a very high quality text and
graphics printer that has a
photosensitive drum that
deposits toner powder on the
paper__________________
a low quality printer that prints by hammering pins on the paper to print an image made up of dots.The hammering action means that it can print on special multipart paper where a number of copies are produced at the same time.
CD-ROM
a compact disk read only memory storage device that is cheap to produce and suitable for storing large amounts of data
The Patient Browser program (GPASS)
discussed in this unit is a type of databasefor sorting and searching patient records. To
UNIT 8 Applications Programs 4"
[search,you select different option screens by
clicking on a tabwith a mouse and inputting
the search criteria (details of what you are
looking for) in text boxes known as criteria
boxes.Different button iconscan be clicked
to perform different operations e.g. the Find
button. The default buttonis the option that
is selected automatically.
Tomb Raideris a popular adventure game
that has appeared in various versions. The
main character is represented by a female
animated image, known as Lara Croft.The
user follows a storyline in which they have to
solve puzzles and control the movements of
the main character, sometimes having to react
quickly to avoid dangerous obstacles. It is
available on well known games consoles
(specialised games computers) called
PlayStationand Dreamcastmanufactured by
a company called Sega.
SimCityis a simulation program(a
program that simulates real life) in which the
user has to develop a city by building roads
and 3D (three-dimensional) buildings, setting
taxes, etc. They also have to control objects
such as simulated cars and people. The user
can download(copy from a server computer)
additional objects and swap items with other
users using a special website. The game is
run on a computer called a Commodore 64
(an early British type of personal computer
particularly suited to games because of its
excellent graphics facilities).
An ASP (application service provider)
rents applications to users i.e. instead of
buying software, the user pays for using
applications as and when they need them. I
The ASP provides the software, manages the hardware and provides storage space, security controls and the physical links to customers. The ASP normally leases storage space for programs and data from data centres(facilities for storing large amounts of information) owned by data storage specialists.
The user is provided with remote access(access across a communications network) to a wide variety of programs including: generic applications such as email(electronic mail) and office suites, high-end(advanced) packages including large, complex business applications such as enterprise resource planning tools (e.g. SAP),business services, such as payroll and accounting systems, expensive specialist tools and e-commerceresources (electronic commerce - buying and selling on the internet).
This gives the user more flexibility and saves them having to install and maintain programs, upgrade(install newer versions of programs), deal with viruses(programs that can reproduce themselves and are written with the purpose of causing damage or causing a computer to behave in an unusual way) and manage email systems(electronic mail systems).
Disadvantages of this system include: the need for a broadband(high bandwidth i.e. a connection with a high signal capacity) network connection or a leased line(a cable connection that is rented for use in a communications system) and dependence on the ASP to provide a secure, reliable, readily available service.
UNIT 9
Multimedia
INTRODUCTION
Multimedia is the term used to refer to a combination of text, graphics, animation, sound and video.
MP3(MPEG Audio Layer 3) is a standard way of storing compressed, digital audio files (usually music). Digital audiois created by sampling sound 44,000 times a second and storing a code number to represent each sound sample. The files are compressed by removing any sounds that are inaudible to the human ear, making them much smaller than files created using other digital audio storage standards, such as WAV.The size of an audio file is commonly measured in megabytes (MB)(millions of bytes). The frequency of a sound is measured in kilohertz (kHz)(thousands of cycles per second). MP3 files have extra code added, called tags,that give the user information about the file e.g. the performer's name, a URL(uniform resource locator i.e. a web address) or a graphic such as an album cover.
Because of their small size, MP3 files are more suitable for transferring across the Internet(the connection of computer networks across the world). Some Internet websites (sets of related pages stored on a Web server on the World Wide Web) are devoted to providing MP3 files for downloading(copying from a server computer to a client computer). The user can create their own music compilations(combinations of files) by listening to each file using a computer program, such as Windows Media Player,and choosing what files to download. They can then use a computer program called an MP3 playerto listen to the files and control the sound. MP3 players let the user group songs into play lists and randomise the selections. They also have sound control features such as spectrum analysers, graphic equalisers, and frequency displays. A track
info buttonallows the user to see the information stored in the MP3 file tag. The appearance of MP3 players can be changed using programs called skins(or themes).MP3 players often include a program, called a ripper,that lets the user rip(extract) a song from a CD (compact disk) and convert it to a standard WAV file. Another program called an encoderis used to convert WAV files into MP3 files or vice versa. Recorderprograms are also available that enable the user to create audio CDs using a writable CD-ROM drive. Special MP3 player devicesare also available that enable the user to listen to MP3 files without a computer.
MIDI(Musical Instrument Digital Interface) is a standard way of connecting musical instruments, music synthesisers, and computers. A piece of electronics called a MIDI interface boardis installed on each device to enable the device to communicate using MIDI standards. As music is being played, it can be displayed on a monitor screen as a musical score, then edited using a computer program that uses all the features of a mixing desk(an electronic device for mixing sounds together), stored and printed. MIDI systems do not store the actual sound. Instead the sound is encoded(stored as MIDI messages)in the form of 8-bit bytes(units of capacity equal to eight binary digits i.e. Is and Os) of digital information. A bitis a binary digit i.e. a 1 or a 0, and a byteis a group of 8 bits. The MIDI messages commonly consist of instructions that tell the receiving instrument what note to play, how long and how loud it should be played, including a number that indicates which instrument to play. Each instrument is represented by a different number e.g. 67 is a saxophone.
A DVD-ROM,commonly referred to as a DVD(digital versatile disk - previously known
as digital video disk), is a development of CD-ROM(compact disk read only memory). It is an optical storage media(a storage media that uses laser light to store data) that provides large amounts of storage space for multimedia files. A DVD-ROM drive(a storage device for reading DVD disks) uses blue laser light (rather than the red laser light used by CD-ROM drives) to read information from the disk. Both sides of the disk can be used for storing files and each side can have two separate storage layers. The data transfer rateof a DVD (the speed that data can be read from a DVD) is also faster than that of a CD-ROM. The capacity of a DVD is commonly measured in gigabytes (GB)(thousands of millions of bytes).
MPEG(pronounced em-peg) is a method of compressing and decompressing video signals. MPEG stands for Motion Picture Experts Group, an organisation that develops standards for audio and video compression.