2. Components of a computer system
- Acomputer systemconsists of a number of interrelated
componentsincluding hardware and softwarethat work together with
the aim of converting data into information.
- In a computer system, processing is carried out electronically,
usually with little or no intervention from a human user.
- The components of a computer system include hardware and
3. Figure 3.1Basic hardware components of a computer system 4.
- Computer hardware describes the physical components of a
- The hardware of a computer system consist sof:
- Central Processing Unit (CPU)
5. Hardware components
- Input device Mouse, Keyboard, Touch screen, another system
- Processor a PCs chip manufactured by Intel or AMD
- Output device screen, printer
- Primary storage Random Access Memory (RAM)
- Secondary storage magnetic (disk drives) and optical storage
(CD-ROM and DVD)
6. Input devices
- Input device are used to capture or enter data into the
- Such data (inhuman-sensibleform) needs to be converted into a
format that supports processing by computer.
- Input devices convert data into a form that makes
7. Central processing unit (CPU)
- CPU is the processor found in a computer system that controls
all of the computers main functions and enables users to execute
programs or process data.
- CPU performs processing by carrying out instructions given in
the form of computer programs.
- Memory (or primary storage) is used as a temporary means of
storage data and instructions.
- Instructions loaded from software which are used to process
data or control the computer system
- Data or information that has been processed
9. Storage devices
- Storages devices provide a means of storing data and programs
permanently until they are required.
- As an example, a program is stored on a hard disk drive until
it is needed.
- When the program is activated, it is transferred from the
storage device into the computers memory.
- When the program has ended or is no longer needed, it can be
removed from memory so that other programs or data can be
10. Output devices
- Output devices translate the results of processing output into
a a human-readable form.
11. Figure 3.2A personal computer labeled with the typical
components 12. Major categories of computers
- A traditional view of computer technology suggests three basic
categories of computer:mainframe, minicomputer and micro-computer
- The physical forms of these different types of system and some
newer types of computers are illustrated in Figure 3.3
13. Figure 3.3Different forms of computer system 14. Mainframe
- Mainframes are powerful computers used for large-scale data
- A traditional view of mainframe computers saw them as large,
extremely powerful machines designed for large-scale
- Examples are those from IBM, Tandem, Amdahl and Hitachi.
- The use of mainframe computers has declined steadily over the
past two decades.
15. Legacy systems
- In many organizations, mainframe computers are consideredlegacy
- Legacy system is a system whichhasbeen superseded by new
technologies or business practices.
- Managers recognize that the existing system may not be entirely
adequate to meet the companys needs, a changeover would be
difficult or even impossible to implement.
- This can be for a number of different reasons:
16. Reasons of retaining mainframe computers
- A lot of investment has been used in developing and maintaining
the mainframe system that a move towards more modern technology
would be prohibited by the costs involved.
- The data and information produced by the mainframe system are
critical to the companys operations
- The links between the existing mainframe system and the
companys major business activities are so strong that it is not
possible to introduce new systems a little at a time.
17. Minicomputers and servers
- The minicomputer combines some of the characteristics of the
mainframe computer and the microcomputer.
- Today, they are often referred to asserversby companies such as
SUN and Hewlett-Packard.
- Different types of server may have different functions, such as
managing a network or hosting a database.
- Microcomputers are considered less powerful than minicomputers
and mainframes, but are more flexible and relatively inexpensive to
- Microcomputers are now often referred to as the client machine
which receives services and data form a server machine forming
theclient/server architecturewhich is a common type of
- Theclient/server architectureconsists of client computers such
as PCs sharing resources such as a database stored on a more
powerful server computers.
19. Types of microcomputers
- In industry, several types of microcomputer are in common
- TheIBM-compatible or personal computer (PC)is considered the
standard for general business use.
- TheApple Macintosh or iMacis often used for professional
desktop publishing applications, such as the production of
- Workstations , such as those produced by SUN, are typically
used in the area of computer graphics. Typical applications include
computer aided design (CAD) and animation.
20. Types of microcomputers
- Desktop computeris intended for office use and supports the
day-to-day activities of an organizations employees.
- These machines tend to be placed in a fixed location and
connected permanently to items such as printers, scanners and other
- Desktop computer is the most common type of microcomputer.
21. Types of microcomputers
- Thep ortable computer is largely self-contained, featuring its
own power supply, keyboard, pointing device and visual display
- Modern portables tend to weigh very little and fit easily into
- Portable computersare often described as notebooks .
- A notebook or laptop is approximately the size of an A4 writing
- Apersonal digital assistant (PDA)can be thought of as a
sophisticated personal organizer.
- A PDA is normally a hand-held device, often no larger than a
- The typical functions of a PDA can include:
- Other features that allow users to store notes such as to-do
23. Organiser/PDA (Continued)
- More sophisticated models such as Palm Pilot or Pocket PC
include a more powerful range of tools, including communications,
spreadsheet and word processing applications.
- Modern computers, PDAs, mobile phones and other devices are
often equipped with a wireless adaptor of some kind.
- One of the most common standards used by wireless devices is
- Bluetooth is popular because it is inexpensive to integrate
into products and is almost completely automatic.
- A Bluetooth adaptor will locate any compatible devices that are
nearby and initiate a connection automatically.
- Another technology used for wireless connections is
- Firewire is often used by computer peripherals that require
very high data transfer speeds, such as digital video equipment and
external hard disks.
25. Network computer
- Network computer (NC)is a computer providing access to a
network system, which to reduce cost features limited disk
storage,aless powerful processor and less memory.
- Network computeris used to provide access to a network system,
such as an intranet or the Internet, at minimal cost.
- The network computer is able to call upon the resources of the
network server, only limited processing power is required.
26. Network computer
- Simple tasks can be carried out by the network computer
- More complex tasks, such as those that make intensive use of a
computers processor, are dealt with by the network server and the
results are passed back to the network computer.
- Also, since software applications and data can be accessed via
the network, only minimal storage capacity is required.
- This type of architecture is calledthin client.
27. Network computer
- Network computers are popular with cost-conscious IS managers
since they potentially reduce thetotal cost of ownership
(TCO)associated with computer systems.
- The TCO describes a range of different expenses incurred by
purchasing and maintaining a computer system.
- Such costs include the original cost of the hardware and
software, upgrades, maintenance, technical support and
28. Network computer
- Network computers act to reduce the cost of ownership in
- The initial purchase costs of hardware and software are
- Since network computers can be managed via a central network
server, administration costs can be reduced. Network computers are
often described as offering the potential to achieve zero
administration, a point where the centralized management and
control of the computers attached to a network server makes
administration costs potentially negligible.
29. Network computer
- Since the network computers contains fewer components than a
conventional personal computer, it is less expensive to maintain,
repair and replace.
- As network computers are often used for a relatively small
number of applications, training and support costs can be
- Components of a computer system
- Major categories of computers
- Selecting storage devices
- Other components of a personal computer
- Selecting hardware suppliers
31. Input devices
- Input devices are used to enter data or instructions.
- The choice of an input device often depend upon the quantity of
data to be entered.
- Data input can be carried out by human operators using input
devices such as mouse or keyboard.
- Large-scale data input may require adirect capture deviceto
acquire and store data automatically.
- There are several different methods for data entry such as
keyboard, mouse, joystick and sound card.
32. Figure 3.4Input devices in context 33. Input devices
- Mouse computers featuring a graphical user interface often
require the use of a mouse or other pointing device. See Figure
- Lightpen a pointing device that can be used to control
applications by pointing to items on the screen.
- Trackball a pointing device that is controlled by rotating a
small ball with the finger- tips or the palm of the hand. Moving
the ball causes corresponding movement to a small pointer on the
screen.Buttons are used to select items in the same way as with the
- Joystick is one of the most common input devices available and
is primarily used for leisure activities such as playing computer
34. 35. Input devices (Continued)
- Optical scanneris widely used for capturing graphics and text
from printed documents.
- It can also be used to perform data entry by converting printed
documents into text files that can be used by word processing
packages and other programs.
- Optical character recognition (OCR)involves using software that
attempts to recognize individual characters.
- A variation on optical character recognition isoptical mark
recognition (OMR)which involves detecting and recognizing simple
marks made on a document e.g. multiple choice answer sheet used in
36. Input devices (Continued)
- Bar code readeris a means of displaying a unique identification
number as a series of think and thin lines. The sequence and width
of the lines in the bar code can be translated into a sequence of
- Bar code numbers are normally produced according to a specific
- TheUniversal Product Code , for example, is a standard method
for creating and using bar codes.
- Abar code readermeasures the intensity of a light beam
reflected from the printed bar code to identify the digits making
up the unique identification number.
- The digits making up the identification number are also printed
at the foot of the bar code.
- The most common example of the use of the bar code reader in
industry is the supermarket checkout.
37. 38. Input devices (Continued)
- Touch screenis a transparent, pressure-sensitive covering that
is attached to the screen of the monitor.
- Users make selection and control programs by pressing onto the
- Touch screens are comparatively expensive and require special
software to operate.
- Common applications for touch screens are interactive kiosks
and bookings systems.
39. Input devices (Continued)
- Graphics tabletis used in the same way as a writing pad.
- A stylus is used to draw images on a rigid pad located near to
- As the user draws with the stylus, the image is duplicated on
the computers display.
40. Input devices (Continued)
- Video capture cardrecords and stores video sequences (motion
video) when connected to a digital video camera or other
- A playback device, e.g. a video cassette recorder, is connected
to the video capture card and special software is used to capture,
edit and manipulate video sequences.
41. Input devices (Continued)
- A sound card can be used to capture sound, music and speech
from a variety of sources.
- A business application is the use of voice recognition software
to dictate text directly into a word processing document.
- The addition of a sound card and CD-ROM device provide a
computer with multi-media facilities.
- Digital cameracaptures and stores still images.
- Images are held in the cameras memory and stored on disk until
they can be transferred to a personal computer.
42. Input devices (Continued)
- Magnetic Ink Character Recognition (MICR)involves capturing
data that has been printed using a special magnetic ink.
- This technology is normally associated with the banking
industry, especially cheque processing.
- Some of the details on a cheque, such as cheque number, are
printed in a special typeface using magnetic ink.
- The shape of each character means that it can be recognized by
its magnetic field.
43. Selecting input devices
- The selection of an input device is usually based upon three
basic criteria: volume, speed and accuracy.
- Record the details of payments made by customersuse more
sophisticated methods such as OMR or OCR.
- Fewer transactionsenter data using the keyboard as an input
44. Selecting input devices (Continued)
- Using OCR and OMR is faster than manual data entry methods
- OCR is generally considered a comparatively unreliable means of
- Error rate is the frequency of errors which occur when using an
input device to recognize patterns.
45. Selecting input devices (Continued)
- Other considerations when selecting an input device are:
- Complexity of data data may need to be interpreted or altered
before they are entered.
- Cost an organization may be unwilling or unable to purchase the
hardware and software required.
- Frequency of data entry some types of data entry may be carried
out on an infrequent or ad hoc basis.
46. Output devices
- Output devices display the results of computer processing.
- The output produced by some devices is temporary in
- A display shown on a monitor when a new image is shown
- A report produced on a printer is more permanent and may last
for many years.
47. Figure 3.7Output devices in context 48. Display devices
- The most common output device is almost certainly the monitor,
formerly referred to asvisual display unit (VDU) or CRT (cathode
ray tube) , that is attached to all personal computer systems.
- The quality of a monitors display can be described in several
49. Display devices (Continued)
- The resolution of the monitor describes the fineness of the
image that can be displayed.
- Resolution is often expressed in terms of pixels (picture
elements) the individual dots that make up an image on the
- A 15 VGA monitor is able to display an image that is 640 by 480
pixels, 800 by 600 pixels or 1024 by 768 pixels in size.
- The number of colors that can be displayed on the screen is
also related to resolution.
- In Microsoft Windows, the typical number of colors that can be
selected through the Control panel ranges from 2 (monochrome)
through 16,256 to 32 million.
50. Display devices (Continued)
- The quality of a monitors display involves measuring the
distance between the pixels on the screen.
- Such distance is called the dot pitch.
- The smaller the distance between pixels, the finer the image
- A dot pitch of 0.28mm is standard and will normally appear
sharp and clear.
51. Display devices (Continued)
- Another indicator of image quality relates to the way in which
an image is displayed on the monitor.
- The number of times the image is drawn upon the screen each
second is known as the refresh rate and is measured in hertz.
- A refresh rate of 60 Hz means that the image will be drawn upon
the screen 60 times each second.
- Aplotteruses a number of different colored pens to draw lines
upon the paper as it moves through the machine.
- The quality of text created is often very poor.
- Plotters are primarily used to create technical drawings, such
as engineering diagrams and to record the progress of continuous
- Laser printer A laser is used to charge sections of a rotating
drum which is then used to print using toner powder achieving a
combination of speed with high print quality.
- Advantages of laser printer are:
- Disadvantages of laser printer are:
- Inkjet printeruses a print-head containing 50 or more small
nozzles. Each nozzle can be controlled individually by
electrostatic charges produced by the printer.
- Characters are formed by squirting small droplets of ink
directly onto the paper.
- Advantagesof inkjet printers include:
- Disadvantagesof inkjet printers include:
- Dot-matrix printer arranges a series of pins (usually from 8 to
24) to form the shape of a required character.
- The character is transferred to the paper by striking the pins
against an ink ribbon. This form of printing is known as impact
printing. Dot-matrix printing is now only commonly used when carbon
copies of a document need to be created.
- Similarly, the daisywheel printer, now seldom used, functions
in much the same way as a conventional typewriter.
56. Factors considered in selecting a printer
- Printing costs the cost of printing is normally described in
terms ofcost per page .
- Print quality is normally measured indots per inch (dpi).This
describes the number of individual dots that can be printed within
a space of one square inch. A typeset document is normally produced
at a quality of between 1200 and 1500 dpi. The typical 600 dpi
quality provided by a laser printer is considered acceptable.
- Paper handling the quantity of paper that a printer can hold is
important. A large paper capacity reduces the need to refill the
- Color printing inkjet printers offer the best compromise
between print quality and cost when producing documents in
- Volume the volume of printing has implications for running
costs, maintenance costs and reliability. Dot-matrix printer (500
pages per month), laser printers (5,000 pages or higher per
- Speed printing speeds are usually measured inpages per minute
(ppm).Typical examples of printing speeds are 1-2 ppm for an inkjet
and 8 ppm and above for a laser printer.
57. Multi-function devices (MFDs)
- New printers that offer additional functions such as scanning,
faxing and photocopying.
- These printers, calledmulti-function devices (or MFDs),often
come with an automatic document feeder, allowing them to scan, copy
or fax as many as 50 pages at a time.
58. Selecting output devices
- Factors that should be considered when selecting an output
59. Storage devices
- Storage devices (Figure 3.8) are used to store programs, data
awaiting processing and the information resulting from computer
- Storages devices are categorized asprimary storagewhen the data
is loaded into computer memory orsecondary storagewhen the data is
stored on a separate device where the information will be retained
even if the machine is switched off.
- Floppy and hard disks are examples of secondary storage.
60. Figure 3.8Storage devices in context 61. Units of data
- Abitis a single binary digit and represents a 0 (zero) or a 1.
The bit is the smallest unit of measurement.
- Abyteis made up ofeight bitsand represents a value between 0
and 255. A byte can be thought of as the amount of space required
to hold a single character.
- Akilobyte (KB)is approximately 1000 bytes.
- Amegabyte (MB)is approximately 1000 Kb.
- Agigabyte (GB)is approximately 1000 Mb.
62. Secondary storage floppy disk
- A floppy disk consists of a plastic disk, coated with a
magnetic covering and enclosed within a rigid plastic case.
63. Secondary storage hard disk drive
- Hard diskdrives are a standard feature of a modern personal
- They are used to store the computers operating system,
application software and data.
- A hard disk drive (Figure 3.9) stores data upon a number of
rigid platters that are rotated at very high speeds. Since the
magnetic read/write heads float above the surface of the platter,
the drive mechanism is enclosed within a vacuum to protect against
dust and other contaminants.
64. Figure 3.9 Different views of the platters and sectors on
hard disk drives 65. Secondary storage flash drives
- Aflash driveis a portable storage device that connects to a
computer via a standard USB port.
- Data are stored in flash memory, in anEEPROM (electrically
erasable programmable read-only memory ) chip that can retain its
contents for as long as ten years before it begins to degrade.
66. Secondary storage CD-ROM
- The CD-ROM drive arose from the audio compact disc player and
began to gain popularity during the late 1980s.
- CD-ROM stands forcompact disc read-only memorydenoting that
CD-ROM discs are read-only devices.
- The data on a compact disc are encoded as a series of dips and
raised areas. These two states represent binary data the same
number system used by microprocessors. The player shines a laser
beam onto the surface of the disc and measures the light that is
reflected back. The intensity of the light that is reflected back
enables the player to distinguish individual binary digits.
67. Secondary storage CD-ROM
- Advantages of the compact disc are:
- A compact disc has a veryhigh storage capacity . A standard
disc is able to store 650 Mb of data. This is equivalent to
approximately 2 million pages of text or 74 minutes of high-quality
- The costs associated with CD-ROM storage are typically very
low. CD-ROM drives areinexpensiveand can be repaired or replaced
68. Secondary storage CD-ROM
- Disadvantages of the compact disc are:
- Compact discs are relatively fragile. They are easily damaged,
for example by accidental scratches or exposure to heat.
- CD-ROM is relatively slow in comparison to other storage
devices such as the hard disk drive.
- CD-ROM is a read-only medium. Although listed as a
disadvantage, this can sometimes be seen as an advantage since
unauthorized changes and accidental erasure of data can be
69. Secondary storage CD-ROM
- A variation on the traditional CD-ROM drive is theCD-recordable
- These drives cannot only read conventional compact discs but
can also write data to special gold or silvered-colored discs.
- Compact discs produced in this way are known as write-once
discs ( WORM ), that is, once data has been stored on the disc it
cannot be altered or erased.
- A more recent development is theCD re-writable (CDRW)drive. In
addition to providing the functionality of the CDR drive, the CDRW
drive allows the use of special compact disc media that can be
written and erased many times.
- It is a cost-effective method of data backup of volumes
previously only possible through tape backup.
70. Secondary storage DVD
- Digital versatile disc (DVD)players began to gain popularity in
1997 and are now fitted as a standard component of many new
personal computers. One common applications for DVD is as a
distribution medium for full-length feature films.
- DVD offers two important benefits to users.
- The disc used by a DVD player offer extremely high storage
capacities, typically between 4 and 7 GB.
- Data held on DVD can be accessed at very high speeds.
71. Secondary storage magnetic tape
- Tape streamer A common form of storage device that used
magnetic tape as a storage medium.
- Major characteristics of magnetic tape include:
- Magnetic tapeallows only sequential access data can only be
accessed in strict order.
- The costs associated with the use of magnetic tape as a storage
medium areextremely low .
- Storage devices based on magnetic tape are consideredextremely
- Magnetic tape are mainlyused for archiving and backup
- Magnetic tape isrelatively fragile and is easily damaged.
72. Primary storage memory
- There are two broad categories of computer memory:volatile and
- The contents ofvolatile memoryare lost when the power to the
device is switched off.
- Non-volatile memoryretains its contents until changed in some
73. Random access memory (RAM)
- RAM is used asvolatile , working storage, holding instructions
and data that are waiting to be processed.
- The contents of RAM are volatile, that is, any data held is
lost when the power to the computer system is switched off.
- A typical computer system will feature 128 or 256 Mb or more of
- In general, the more RAM a computer system is equipped with,
the faster it will operate and the more powerful it will be in
terms of the complexity of the programs it can run.
- RAM is also found in a number of other devices, for example in
a printer RAM is used to store an image of the document to be
74. Read-only memory (ROM)
- The contents of read-only memory (ROM) are fixed and cannot be
- ROM isnon-volatilemaking it ideal as a means of storing the
information needed for a device to function properly.
- In a computer system, the basic information needed so that the
computer can access disk drives and control peripherals is stored
in ROM preventing users from accidentally deleting or altering
information essential to the computers operation.
75. Selecting storage devices
- The selection of a storage device will normally be based upon
speed, storage capacity and cost.
- Reliability of a storage device
76. Storage-type summary ofselection criteria 77. Selecting
- The speed of a storage device is usually measured in terms of
its access time (sometimes known as seek time) and data transfer
- Theaccess timerefers to the average time taken to locate a
specific item of data.
- Access time are normally given in milliseconds, for example a
typical hard disk drive might have an access time of 11ms
- Thedata transfer ratedescribes how quickly the device is able
to read continuous blocks of data. It is normally expressed in
terms of kilobytes or megabytes.Typical data transfer rate for a
CD-ROM drive might be given as 900 kb per second, while a hard disk
drive might transfer more than 6 Mb per second.
78. Selecting storage devices
- The storage capacity of a given device will measured in
kilobytes, megabytes or gigabytes.
- In general, a fixed storage device will operate faster than one
that uses removable media.
- Many applications generate large data files that cannot be
stored conveniently on removable media.
79. Selecting storage devices
- The costs associated with storage devices are normally given in
terms of cost per megabyte.
- In some cases, the cost per megabyte is based upon the cost of
the hardware (e.g. hard disk drive), in others it is based upon the
cost of media (e.g. floppy disk).
80. Selecting storage devices
- Reliability of a storage device
- A hardware failure might prevent all access to important
- Errors introduced when storing or reading data might also have
- Permanence of storageis important if there is a need to protect
data from being deleted or altered.
- Security measuresare necessary to prevent data from being
stolen or damaged.
- Removable media can be transported easily
- Fixed devices are less vulnerable but also less versatile.
- TheCentral Processing Unit (CPU) or processor uses instructions
from software to control the different components of a PC.
- CPU found within a computer consists of two components:
- an arithmetic logic unit (ALU).
- Thecontrol unitcontrols the operation of all hardware,
including all input/output operations.
- TheALUcarries out arithmetical calculations, for example,
addition and can also make comparisons between values.
82. 83. Processors
- The speed of a processor will depend upon a number of different
- Two such factors are clock speed and bus width.
- Theclock speed(measured in MHz) determines how many
instructions per second the processor can execute.
- Thebus widthdescribes how many pieces of data can be
transmitted at one time.
- In both cases, the higher the value, the more powerful the
- For example, clock speeds for the Pentium range of processors
have varied from 60 Mhz in early versions through to several GHz in
more recent versions (Table 3.2).
84. Table 3.2Historical improvements inprocessor capability Date
Name Transistors and microns Clock speed in MHz MIPS (millions of
instructions per second) 1974 8080 6k ,6 2 0.64 1979 8088 29k, 3 5
0.33 1982 286 134k, 1.5 6 1 1985 386 275k, 1.5 16 5 1993 Pentium
3.1M, 0.8 60 100 1997 Pentium II 7.5M, 0.35 233 400 1999 Pentium
III 9.5M, 0.25 450 1000 2001 Pentium 4 42M, 0.18 1500 1500 85.
- Not all aspects of performance of a computer are governed by
- As a general rule, the faster the processor, the faster and
more efficient the computer.
- Virtual memory, RAM capacity, had-disk speed and graphics cards
can also have a significant impact on overall system speed.
86. Graphics card
- Agraphics cardenables a computer to display text or graphics on
- The graphics card prepares and stores the image in memory prior
to showing it on the screen.
- When the image is complete, it is transmitted to the monitor
87. Graphics card (Continued)
- Amount of memory available to a graphics card determines
themaximum resolution of the imageandhow many colors can be
- All graphics cards support theVGA (video graphics
array)standard which specifies a maximum range size of 640 by 320
pixels, displayed in 16 colors.
- A VGA display can be achieved with just 256 kb of memory but
larger images with more colors can require 1 Mb of memory or
- Many graphics cards are supplied with 64 Mb, 128 Mb, or even
256 Mb of memory, allowing them to display very complex images at
88. Graphics card standards 89. Motherboard
- Themotherboard(Figure 3.12) is the main circuit board within a
computer and houses the processor, memory, expansion slots and a
number of connectors used for attaching additional devices, such as
a hard disk drive. Any device that forms part of the motherboard is
able to communicate with the processor directly.
- The motherboard will contain a ROM chip that holds the
computers BIOS. The BIOS (basic input/output system) contains
software that controls all of the computers most basic
- It is the BIOS that allows the keyboard, display, hard disk
drives, serial ports and other devices to function.
- The BIOS is stored in ROM so that it is always available and
cannot be accidentally damaged or erased.
90. 91. Motherboard (Continued)
- Storage devices, such as hard disk drives, are attached via the
motherboards I/O (input/output) connections.
- At least twoserial portsare also supported, allowing mouse,
modems, printers and a range of other devices to be connected.
- In addition,a parallel portis normally used to connect a
printer, scanner or other device.
- Expansion slotsallow additional devices to be connected to the
- A computers capabilities can be extended by adding special
circuit boards (known as expansion cards) to the motherboard.
- Commonexpansion cardsinclude graphics card, modems and sound
cards (Figure 3.13)
- A typical computer will feature up to six expansion slots.
92. Figure 3.13A typical expansion card for use with a personal
computer 93. Selecting hardware suppliers
- The process of selecting a supplier for hardware is often known
asvendor analysis .
- Large purchases may involve the organization in producing
atender document .
- A tender document is an invitation to suppliers, asking them to
bid for the right to supply an organizations hardware, software and
- An organization selects a supplier by examining each response
to the invitation to tender in detail.
- Tender documents will ask for important information about
- Size of the organization (staffing, premises, turnover,
- Number of years of experience
- Details of any major projects undertaken
- Details of any previous customers who may be willing to provide
95. Evaluating proposals
- There are three basic criteria for evaluating a suppliers
proposals. These are based ontechnical, cost and support issues
- Technical issuesrefer to the extent to which the proposal
satisfies the hardware and software requirements set out in the
tender document or statement of requirements. They include:
- Performance : whether or not hardware will perform as
- Compatibility : equipment is compatible with the companys
existing systems, particularly any software packages already in
96. Evaluating proposals (Continued)
- Cost issuesdescribe the overall cost of the project, including:
installation, ongoing maintenance and factors involving methods of
- Consideration must be given to different costs associated with
the purchase of a new computer system.
- Initial cost covers the purchase of hardware, installation and
- Ongoing costs include insurance and maintenance and are paid
over the life of the system. Ongoing costs are known as thetotal
cost of ownership (TCO).
97. Evaluating proposals (Continued)
- Support issuesdescribe the reputation of the supplier in terms
of their ability to provide adequate support, training, advice,
repairs and maintenance.
- Training offer a range of training courses that cater for mixed
abilities and enable users to reach different levels of
- Maintenance --- suppliers should guarantee that important
repairs are carried out within a fixed time period.
- Implementation The use of a single supplier can ensure that the
project runs more smoothly and simplifies the division
- Backup facilities a backup or disaster recovery site reproduces
an organizations computing facilities in order to provide a measure
of protection against a major breakdown.
98. Evaluation methods
- Benchmarkingdescribe the process of testing the performance of
- Having carried out a series of benchmark tests, the results can
be compared against similar items in order to make the best
- The requirements are used to devise a list of criteria for the
selection of a given piece of hardware or a supplier.
- The relative importance of each factor is determined by a
- Each item or supplier is assigned a series of scores based on
the criteria in the weighted ranking table.
- The total score for each item or supplier is calculated and
used as the basis for final selection.
99. Evaluating proposals (Continued)