Computer notes revised

Define a computer
 A computer is an electronic machine that works under the control of stored programs to
accept, process and output data/information for use by the operator.
 A device that accepts data, processes the data in accordance with a stored program, generates
the results, and usually consists of input, output, storage and arithmetic, logic, and control
units.
 A functional unit that can perform substantial computation, including numerous arithmetic
operations or logic operations, without human intervention during a run.
Computer program:
o A set of instructions, written in a specific programming language, which a computer follows
in processing data, performing an operation, or solving a logical problem. Also see
software.
o A computer program is a set of statements or instructions to be used directly or indirectly in
a computer in order to bring about a certain result.
The hardware components of a computer system
• Input devices
• Output devices
• Main memory
• Processing hardware
• Storage devices
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A diagram showing the components of a computer
The CPU consists of the ALU & CU
Key
Data flow
2 way data flow
Command flow
Describe the functions of each component.
Define the term hardware and give examples.
Computer hardware
• Hardware refers to the physical/tangible components (parts) of the computer system.
• Hardware comprises all of the physical parts of a computer, as distinguished from the data it
contains or manipulates, and the software that provides instructions for the hardware to
accomplish tasks.
Computer software
Define computer software and give examples.
Software is the name given to the instruction which make a computer work.
Software refers to the set of step by step instructions that tells the computer what to do, when and
how to it.
Program software performs the function of the program it implements, either by directly providing
instructions to the computer hardware or by serving as input to another piece of software.
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Control unit- issues
commands to computer
elements and interprets
stored instructions
Arithmetic & logic unit-
performs computations and
logic operations
Input Unit
Data &
instructions
Output Unit
Information
after processing
Main Memory
Holds data & instructions &
results of processing
Backing/Auxiliary storage
Supplements the main
memory
2

Types of computers
Basic computer types
Digital computers
They process discrete data values (0 1 2 3), operating on it in steps e.g. counting of our fingers is
simplest digital operation. Examples includes digital watches, fuel pumps
Analog computers
These process data in the form of electrical voltages which variable positions of a pointer on a dial.
Output is in the form of smooth graphs from which information can be read. Examples include volt
meters, speedometer
Hybrid computers
They combine the features of basic digital and analog computers.
Purpose classification
Special purpose computers
They do a particular job to solve problems of restricted nature. E.g. digital watch computers,
programmable petrol pumps
It is used in weapon guidance
General purpose computers
These solve a wide range (variety) of problems; can be adapted to perform particular tasks or solving
problems by means of specially written programs.
Classification by usage
Word processor
This is a special purpose computer used in the production of office documents, letters, and contracts
– does text.
Personal computer (PC)
A microcomputer designed for independent use by an individual at work/home mainly for business
purposes. Some are portable; they can be connected to a minicomputer or mainframe computer to
gain access to larger machine facilities.

Home computer
This is a low cost microcomputer of limited capabilities; programs are designed for domestic uses
e.g. computer games and for controlling family finance.
Desktop computer
Desktop computer are designed for use on a desk in an office environment e.g. home computer, PC
Workstation
• This is another type of a desktop computer.
• Larger and powerful PC can be workstations.
• They have advanced features which are not found on PCs; these are in-built capabilities for
interconnection and processing pictorial and text data types
Laptop computer
The laptop computer is sufficiently small and light for the user to comfortably use it on the lap. It
operates from mains electricity/rechargeable battery. These are small enough to fit in a brief case,
have in-built disk drives and flat screen. The later ones are mostly liquid crystal display (LCD) –
gives clear pictures.
Imbedded computers
As the name implies, they are imbedded devices or systems which are not accessed directly; e.g.
within petrol pumps, watch, cameras video recorders, and many types of domestic and industrial
equipment, cell phones, microwave cooker, Compact Disk changers etc. They are hard wired into
another device and dedicated to a specific purpose.
.
Computer categories
 Supercomputers
 Mainframes
 Minicomputers
 Microcomputers
Supercomputers
◊ Describes a category of extremely powerful computers specifically designed for high speed
numeric computations.
◊ The computer can process hundreds of millions of instructions per second.

◊ High capacity computers capable of executing instructions faster than mainframe and are
extremely expensive.
◊ The speed of executing these instructions generates extreme heat, and therefore the
computers require special cooling system to operate.
◊ Uses include weather forecasting, scientific and mathematical research, and design of high
speed aircraft and space exploration.
Mainframes
◊ Mainframes are large, powerful computers that are physically larger than micros and minis
and usually have one or more central processors with faster instructions processing speed.
◊ They typically process hundreds of millions of instruction per second.
◊ Mainframes have large primary storage capacity.
◊ Many Mainframe models have ability to service hundreds of users at once.
◊ Some commercial organizations require large amounts of data to be processed in the least
possible time and Mainframes allow them to perform such functions
◊ Uses of Mainframes include: data warehousing, commercial airline ticketing and
reservations, government record keeping and financial servicing.
◊ Application categories: host computers, database servers and transaction processors.
Minicomputers
◊ Minicomputers are larger and more powerful than most microcomputers but are smaller and
less powerful than most Mainframe computer system.
◊ Serve in industrial process-control manufacturing plant computers and play a major role in
CAM
◊ Also take the form powerful technical workstations for CAD applications
◊ Often used as front-end processors/computers to help Mainframe computers control data
communications networks with large numbers of data entry terminals.
◊ Also used as powerful network servers to help manage large interconnected LANs that tie
together many workstations.
◊ Downsizing is a term that was commonly used in the early nineties when smaller computers,
capable of much of the functions of Mainframes, began capturing the market.
◊ Minicomputers are suitable for mid-sized companies that require the computing power of
Mainframes to be efficient and at the same time be cost effective.
◊ Users of minis would be smaller banks and financial institutions, supermarket chains and
departmental stores.
◊ Application categories: network servers and application systems
Microcomputers
◊ We refer to a microcomputer as a personal computer or PC.
◊ Microcomputers categorized by size include: Desktop
◊ Most PCs are single user computers, perform a diverse range of functions and can be further
classified by size e.g. desktop, laptop, palmtop

◊ The late nineties have seen a huge influx of microcomputers whose sole aim was to provide
affordable computing power to the general public.
◊ They are now used as Network servers. The demand for microcomputers and the change in
microchip technology have produced cheaper computers that are affordable to students and
the general public.
◊ Can support CAD
◊ Users of PCs range from students, who use them for word processing to a salesperson who
depend on the PC for information.
◊ Network servers are powerful microcomputers that controls and coordinates communication
and resource sharing in LANs of interconnected PCs and other devices.
◊ NB: there is a farther step in miniaturization, various integrated circuits (I.Cs) and elements
of a computer are replaced by a single I.C called a chip. The continuing and rapid
technological advancement have affected the whole computer industry.
Factors to consider when buying a personal computer
Shopping for a personal computer (PC) can be enjoyable, or it can be frustrating. Unfortunately,
some shoppers believe all personal computers are alike, so their main objective is to find the
cheapest one. Doing so can be a mistake. The old saying ‘you get what you pay for’ is true. Many
buyers have later discovered that the computer they bought/purchased lacked important components
and features. Avoid making this mistake! The following section helps you in your search for the
right PC.
Plan before you buy
Before spending your money, prepare a written list of your computing needs and how and
where you will be using your new system. The following is a list of questions that will help
you identify your computing needs:
1. How much can I afford to pay for a computer?
Prices of personal computers range from a few hundred to thousands of dollars. Faster and more
feature-rich PCs are usually more expensive. Also personal computers soon become obsolete;
within a few years you may want or need one that is faster and more versatile.
2. Where my new PC would be used?
If you would be using it only in your home or office, a desktop computer would be suitable.
However, if you would want to take it with you, you should consider purchasing a laptop
(notebook) computer weighing 4 pounds or less.
3. Which applications would I run on my computer?
Make a list of applications for which you plan to use your PC. For example, will you use your
computer to prepare letters and reports? Or Analyze numeric and financial data? Or prepare
visual presentations? Or access the internet? Or listen to music? Or create and work with
graphics?

4. How long will I keep the computer?
Try to estimate the length of time (years) you will use the computer before buying the next one.
If you expect to use your PC for several years or if you think you may later want to add new
applications, consider one that is expandable, so you can add new components, such as the
modem, printer, or add-on boards. Make sure the PC has expansion slots so you can connect
these devices to your PC.
5. Check out the manufacturers and seller’s reputations and warranties and
become familiar with various brands and models.
Talk with friends, co-workers, classmates, teachers, and significant others about their PCs. Ask
about the performance of their PCs and get recommendations from persons you trust. Eventually
you may need to have your PC serviced. Ideally, the vendor has a service department that can
repair your PC. If not, you may need to locate a third-party to provide this service.
6. PC architecture
PC architecture refers to the design and construction of the PC and its systems unit, and all
architecture not are the same. For example, the architecture of an Apple Macintosh PC differs
from that of an IBM or IBM compatible PC. Therefore, software written for an Apple Macintosh
PC may not run on an IBM or IBM compatible PC. Although some users prefer a Macintosh PC,
much more software is available for IBM and IBM-compatible PCs.
7. Microprocessor
Selecting the right microprocessor is extremely important. Processing speed, measured in
megahertz (MHz) or gigahertz (GHz) is probably the first consideration. The higher the number
of MHz or GHz, the faster the processor will manipulate data. If speed is important, consider
choosing a processor with a speed measured in GHz. PCs containing microprocessors with
speeds up to 1.5 GHz and higher are available (dual core).
8. Main memory
Main memory (RAM) is needed for the temporary storage of programs and data while data is
being processed. Some application software requires a considerable amount of RAM to function
properly, and newer software versions usually require more RAM than older versions. Typical
PCs now come with 1 GB or more of RAM; older versions may have 64MB, 128MB or 512MB
of RAM. Be sure the PC has sufficient RAM to run the software you will be using.
9. Secondary storage
What type(s) and amounts of secondary storage are you likely to need? Typical old computers
come with floppy disk drive and hard disk drive already installed. A standard diskette can store
up to 1.44MB of data, although other types of diskettes are available that provide greater storage
capacity. A hard disk drive contains one or more rigid storage platters and provides for the
permanent storage of considerably more data. However, the disk itself cannot be removed from
the drive. The storage capacity of a hard disk is an important consideration because it is used to
all the systems and applications software. Typical hard disk capacities are 20, 40, 60, 80, 350 GB
and more. Be certain the PC you considering has sufficient secondary storage capacity for your
needs. Other secondary storage media are available. DVD-RAM drives provide for high storage

capacities. Most software publishers store their programs on CD-ROM because of the high
storage capacity and because CD-ROMs operate faster than floppy disks. (Diskettes are almost
obsolete). If you will use your PC to play movies, your computer should include a DVD (digital
versatile disk) drive. If you will work with large files, consider purchasing a computer that
includes a CD-RW drive. A CD-RW disk is a reusable high capacity disk that allows you to store
huge amounts of data and to erase data that is no longer needed. USB disk drives have gained
popularity as of late. USB disk drive is a portable storage device that has much more storage
capacity than the almost extinct floppy disk, but is small and light weight enough to be carried
(transported) on a key chain or in a pocket.
10. Ports
The number of ports (slots) available inside the systems unit determines the number of add-on
boards that can be installed inside the systems unit. For example, you cannot connect a printer to
your computer unless your computer is equipped with an appropriate port (slot). Be sure the PC
contains the necessary slots for the add-on boards and peripheral devices you will be using with
your computer.
11. Input devices
Typical input devices are the keyboard and the mouse, although other kinds of input devices are
available. Most keyboards and mice operate similarly. However, there are slight differences on
how each ‘feels’ to the user. Before buying a PC, you may want to test the keyboard and the
mouse for comfort and ease of use. Some sellers will allow you to exchange the keyboard or
mouse that comes with the computer for a different one.
12. Output devices
Output devices produce output in either soft copy or hard copy form. Most PCs come with a
monitor (for soft copy output), but you may purchase a hard copy output device, such as a printer
separately.
13. Monitors
There are wide differences among PC monitors, perhaps with resolution being the most
important variable. Resolution refers to the clarity of text and images being displayed. Before the
purchase, carefully evaluate the monitor’s resolution. Many vendors allow you to choose from
monitors of varying resolutions. A resolution of 1024 by 1024 is considered high resolution, in
which text and images display exceptionally clearly. High resolution monitors are typically more
expensive. Monitor size is another important consideration. Viewing areas range form 15
diagonal inches to 21 inches and higher. Larger monitors are usually more expensive, but may
worth the extra cost. For example, an individual with weak vision may prefer a larger monitor. If
your desktop space is limited, consider purchasing a flat-panel monitor which occupies less
space. However, flat-panel monitors are more expensive than standard monitors of the same size.
14. Printers
Two popular types of printers are inkjet and laser, both of which are versatile and capable of
producing high quality output in color. Examine a variety of printers and models and check the

price and output quality of each type and model. Most inkjet printers are quiet, produce high
quality output and are relatively inexpensive although the ink cartridge they use can be
expensive. Print resolution is an important factor to consider. Some offer impressive resolution
and can produce output of amazing color.
Laser printers are fast and can produce high quality output in both black and color tones. Color
laser printers are more expensive than those using only black toner. The color laser printers cost
range from a few hundred to thousands of dollars. Choose printer to match your needs list.
You have been delegated the task of selecting a new printer from a range of different options
currently on the market. The machine has to serve a small network of microcomputers in your office.
Software used includes a word processing package, database, spreadsheet and a presentation
packages. Assuming that cost is not a major constraint, list 10 features of the printers which you
would evaluate in your investigation.
1. Print quality, for example the print from a dot matrix printer varies with the number of pins and
even the best are inferior to laser printers.
2. Character formation, whether made from dots as in matrix printers or full characters as with
daisy wheel or laser printers.
3. Multi-part, i.e. whether several copies can be printed at once as with impact printers.
4. Fonts or typeface, early computer users were satisfied with any quality whatsoever, but the
advances into areas such as word processing and desktop publishing have stimulated a demand
for varying type faces or fonts within the same document.
5. Letter quality, whether the quality is equivalent or superior to that of a good typewriter and so
acceptable for the word processing of mail. Some printers have a choice of two print modes,
draft quality and letter quality.
6. Speed in terms of characters per second
7. Graphics capabilities
8. Flexibility, for example, is it suitable for one task only, such as good letter quality but not
graphics, as with daisy wheel printers, or good graphics but slow speed and indifferent letter
quality as with some of dot matrix printers.
9. Sheet feeding, in terms of single sheets, friction or sprocket feed.
10. Capital cost or what it costs to buy
11. Running cost or what it cost in ribbons, print toner, ink cartridges, special stationery and
maintenance.
12. Compatibility with standard packages; many programs support a range of printers by generating
the correct control character fonts, features like italics and underline, and for graphics.
13. Robustness; some very cheap printers are ideal at home but would not last very long in an office.
14. Reputation of the manufacturer as a supplier of printers.
Necessary conditions for an ideal computer room environment
1. Cleanliness: books, manuals not encouraged because they bring with them dust and caught fire
easily
2. Air conditioners, which control the room’s temperature and humidity levels
3. It should be dust free; dust is the biggest ‘killer’ of hard drives
4. No carpets for they caught fire more easily
5. You are not allowed to eat, smoke or drink in the computer room
6. No magnetic material should be in the computer room

7. The computer room should be located in such a way that the computers are not exposed to direct
sunlight or hot environments; use curtains if otherwise.
8. The computer room must be fitted with burglar bars, alarm systems, and/or guarded 24 hours to
ensure security.
9. The computer room should have surge protectors or suppressors to guard against electrical faults
and high voltages
10. The computer room should have uninterrupted power supply (ups) in case of power failures
which may be fatal.
Privacy, integrity and security of data
Privacy
◊ Is the right of people not to reveal information about themselves.
◊ Is the basic democratic right but Information Technology (IT) present constant threat to this
right.
Data integrity
- Means making sure that the data is correct.
- Input data has to be verified and validated to ensure its integrity.
Data verification
- Refers to a check to see if data has been entered correctly.
- Data verification is where data input to the computer system is re-entered by a second
independent operator for machine comparison with the initial entry.
Data validation
- Data validation is where data is checked to see if it is sensible in the context in which it is
being used.
- Refers to the process of checking by means of a computer program whether input data is
valid or permissible.
- Data validation is a process of checking that the data which is input to a program is valid.
- Validation process can go on to exercise some power of judgement on the completeness and
reasonableness of the input data.
Invalid data can arise in many ways especially when the data preparation stage involves the copying
and/or transcribing of data before it is input errors are prone to occur.
Data security/protection
• Data security means making sure that data is not misused or observed by the wrong
people.
• Data security refers to keeping data safe from various hazards or dangers like natural
hazards, deliberate corruption or destruction of software and hardware by malicious
or terrorist acts, illegal access to data by hackers/crackers (people who break into the
system) and accidental destruction by hardware or software failure or operator’s error.

Functions of data security/ data security functions
o To prevent loss of data files
o To secure data from accidental or deliberate corruption or modification (data integrity)
o To prevent data from accidental or deliberate disclosure to unauthorized individuals.
o To protect the rights of individuals and organizations by restricting access to information
which relates to them and is of private nature to those entitled or authorized to receive it (data
privacy).
Data protection act 1984
 The act was passed to prevent the misuse of personal data (on employees, customers,
potential customers and others) and to prevent it causing harm to individuals.
 Computer Bureau is a broad term covering anyone processing personal data on someone
else’s behalf.
The data protection act 1984 has clauses to ensure that:
1. Personal data must be obtained legally and fairly as well as being processed fairly and
lawfully.
2. Personal data may only be held for one or more specified and lawful purposes
3. The data must accurate and (where necessary) kept up-to-date
4. An individual is entitled to examine data held about him/her and have it corrected where
necessary or erase such data.
5. Personal data must not be used or disclosed in any manner incompatible with original
purpose of its collection.
6. personal data must be adequate, relevant and not excessive in relation to that purpose
7. it must not be kept for longer than is necessary
8. Individuals must be informed by any data user that they hold information on them and must
inform them at reasonable intervals and without overcharging for the service.
9. appropriate security measures shall be taken against unauthorized access, alteration,
disclosure, or destruction of personal data and must also be taken against accidental loss{or
destruction of personal data}
10. (Individuals on whom data is held are data subjects) the act gives these individuals the right
of access to the information, the right to challenge inaccurate information and the right to be
compensated if they suffer harm.
Some exceptions to the right to receive compensation
- where data has been supplied by the individual
- where data has been acquired with reasonable care
- data held for statistical purposes, from which it is impossible to identify individuals
Note: The main danger with computerized data is that the large volume of data can be sent
anywhere in the world at very high speed and at little cost, whereas it would be so time
consuming and expensive to photocopy and post manual files of information to other
organizations (this is unlikely to happen). Therefore, there is no need for similar legislation
for non-computerized data.

Measures to ensure data security
1. Data encryption
• Data encryption refers to the process of scrambling or hiding the substance of information so
that it cannot be understood without the key necessary to change it back to its original form.
• Data encryption refers to the process of scrambling or hiding the substance of information so
that it cannot be understood until it is decrypted or deciphered to change it back to its original
form.
• Data encryption refers to any process used in cryptography to convert plaintext into cipher
text in order to prevent anyone except the intended recipient(s) from reading the data. There
are many types of data encryption; they are the basis of network security. Common types
include Data Encryption Standard and public key encryption.
• Encryption is the process of transforming a message in ordinary language i.e. plain text to
produce cipher text which is then sent along a communications link/line. The receiving
computer uses another transformation code to decode/decrypt the message.
• Encryption is the process of disguising a message or data in such a way as to hide its
substance (meaning).
Data encryption/decryption
Data is coded before transmission over WAN and decrypted only if you have the key and code to
decrypt the data on receiving the end.
Encryption provides a last line of defense against unauthorized use of data. If data is encrypted,
unauthorized users obtain only scrambled gibberish instead of meaningful information.
Decryption refers to the process of converting encrypted content back into its original form i.e. the
process of converting cipher text to plain text.
Cipher text refers to the unreadable characters (content) that plain text is converted into for security.
2. Firewall
• Firewall refers to software designed to prevent unauthorized access to a PC or network
through a connection to the internet.
• Firewall is a security system that acts as a protective boundary between a PC or network
(intranet) and the outside world.
• Internet Connection Firewall (ICF) is firewall software that is used to set restrictions on what
information is communicated from your home or small office network to and from the
internet to your network.
• Firewall is a system of hardware and software that blocks unauthorized users inside and
outside the organization from entering the intranet.
• The firewall works by monitoring all data sent to and from the PC and comparing the data
with the set of user defined security criteria. Any data that does not meet those criteria is
blocked.
• Firewalls also process encrypted data and verify the validity of the user. Users would require
access to the firewall before they can transmit data.
• Latest firewalls also have the ability to detect virus software in packets of data that is sent
through the network. Firewall disallows data transmission if it detects strains of virus on the
data being transmitted. Security is essential to an intranet.

A firewall consists of two parts; a choke and a gate
• The choke forces all data packets flowing between the internet and the intranet to pass
through the gate
• The gate regulates the flow between the two networks. It identifies authorized users, searches
for viruses, and implements other security measures.
• Thus intranet users can gain access to the internet (including key sites connected by
hyperlinks) but outside internet users cannot enter the intranet.
Photonics is the science of sending data bits by means of light pulses carried on hair-thin glass
fibres.
Wave division multiplexing/dense wave-length division multiplexing allows laser pulses of different
hues to be sent down the same tiny fiber.
There are three methods of personal identification: something a person carries, something a person
knows, or some unique physical traits. Any one of these methods has the potential to positively
identify a person, and each has a unique set of advantages and disadvantages.
3. Usernames and passwords
• Password is a string of characters that must be provided before a logon name or an access is
authorized.
• Password is a security measure used to restrict logon names to user accounts and access to
computer systems and resources.
• Passwords restrict only authorized personnel/users to have access to the data or computer
rooms
• Passwords brings in an aspect of accountability, if a file is deleted, the person with the
password will be reported as the culprit through logging.
• Passwords are widely used by companies to protect their equipment and data but can be
forgotten.
• Password can be made up of letters, numbers and symbols and it is case sensitive.
Password cracking software uses one of the three approaches
o Intelligent guessing-this refers to dictionary attacks (a brute force method of trying every
word in an electronic dictionary) and automation that tries every possible combination of
characters. Nevertheless, the success of this method decreases if a password is based on two
words, a word and a number, or a nonsense word that does not appear in a dictionary.
o Given enough time, the automated method can crack any password even though it can still
take months to crack a strong password.
Encrypted passwords
Encrypted password is a password that is scrambled. Encrypted passwords are more secure than
plaintext passwords, which are susceptible to network sniffers.
Protecting your password
To ensure security, passwords must be used carefully.
Recommendations that help protect your password
o Never write down your password especially in obvious places

o Never share your password with anyone
o Never use your network logon password for another purpose
o Use different passwords for your network logon and the administrator account on your
computer and don’t choose obvious passwords; for hackers can break in.
Strong passwords may contain at least seven characters from all the groups (letters, numbers, and
symbols), one symbol character in the 2nd
through sixth position. The password should significantly
different from prior passwords. The password must not contain your name or username or a common
word or name.
4. Authorized entry to computer installations
• Most installations have card readers, voice recognition systems or keypads that prohibit entry
to unauthorized personnel. Apart from access codes and other methods, lock and key is also
used to restrict entry into computer installations
5. Backing up files on external disks periodically
The backup copies of the files must be kept in a different location and make about 3 generations
of backup
6. Saving work frequently
7. Avoiding viruses
8. Installing fire alarms
9. Lining computer rooms with fire resistant material
10. placing the computer room in upper rooms of the building to avoid floods and reduce burglaries
11. having a security guard 24hrs a day
12. Biometrics
• Biometrics refers to the biological measurements, such as fingerprinting, that are used in the
context of computers to verify a person’s identity.
• Biometrics is the technology of authenticating a person’s identity by verifying a personal
characteristic.
• Biometrics device grant users access to programs, systems, or rooms by analyzing some
physiological (related to physical or chemical activities in the body) or behavioral
characteristics which include fingerprints, hand geometry, facial features, voice, signatures
and eye patterns (the patterns of blood vessels in the retina of the eye).
• Fingerprint scanner (the most widely used biometric device) is a biometrics device that
captures curves and indentations of a fingerprint and compares them with those of a stored
image.
Biometric device
• Biometric device authenticates a person’s identity by translating a personal characteristic
(e.g. fingerprint) into a digital code that is then compared with a digital code stored in the
computer verifying a physical or behavioral characteristic.
• If the digital code in the computer does not match the personal characteristic code, the
computer denies access to the individual.
• Grant access to computers, programs, or rooms using computer analysis of some biometric
identifier.

• Examples of biometric devices and systems (technologies) include fingerprint scanners, hand
geometry systems, face recognition systems, voice verification systems, signature
verification systems, iris recognition systems and retinal scanners.
Advantage
• Biometric data can’t be lost, forgotten or borrowed
• Some biometric technologies are cheap and can confirm your identity in less than two
seconds, even from a pool of thousands of employees. Fingerprint scanners cost less than
$200.
13. User rights are rules that limit the directories and files that each user can access. The system
administrator gives the computer users rights that allow them to access only certain directories
and files when creating the user accounts on the computer system or network. Granting users
only the rights they need helps prevent both accidental and deliberate damage to data. If users are
granted limited rights, a hacker/cracker who steals someone’s password has only those rights
granted to the person from whom the password was stolen. Hackers occasionally gain
unauthorized access to computer systems through a trap door. A trap door is a special set of
instructions that allows a user to bypass the normal security precautions and enter the system.
Trap doors are often created during the development of a new system to provide the system
administrators with easy access to the computer for installation and testing. All trap doors should
be removed before the system becomes operational, if not removed; it becomes a possible means
of entry for any hacker/cracker that/who discovers it.
14. Technical control: security dial back devices can eliminate the problem of access by
hackers/crackers and former employees. Dial back systems prevents unauthorized outsiders from
breaking into company’s information system microcomputers and phone lines. When someone
dials the computer by touch tone phone and gives a password upon requested by the computer,
the computer disconnects the caller, checks its files and dials back the authorized telephone
number indicated by the password in the files. If the call came from an unauthorized number, the
computer dials the authorized location and warns the user that there has been an attempt to use
that password.

A videoconference (videotele) is a set of interactive telecommunications technologies which allow
two or more location to interact via two-way video and audio transmissions simultaneously.
It has been called visual collaboration and is a type of groupware.
VC adds another possible alternative and can be considered when
- A live conversation is needed
- Visual information is an important component to the conversation
- The parties of the conversation cannot physically come to the same location or
- The expense or time of travel is a consideration
Deaf and hard of hearing individual have a particular interest in the development of affordable high
quality VC as a means of communicating with each other in sign language.
Video Relay Service one sign language, the other spoken
- Mass adoption is low
- Complexity of system
- Perceived lack of interoperability
Computer conference
- Instant messaging
- Chat systems –one-to-one, instant messengers, internet relay chat, talkers, MUDs, MUCKs,
MUSHes & MOOes
Chat-informal conversation
E-mail-delivered any time, incoming mail can be immediately printed, saved to disk, replied to,
forwarded or deleted.
- Good to make appointments for busy people
• e-mail can compromise the security of the organization because sensitive data/information
can be easily distributed accidentally or deliberately. E-mail should be entrusted to well
trained and trusted staff members
• can be impersonal or misunderstood
• cultural differences can lead to misunderstandings emanating from different interpretation of
certain words.
Magnetic disks
- Use magnetic particles to store items such as data, instructions and information on a disk
surface.
- Depending on how the magnetic particles are aligned, they represent either a o bit or 1 bit.
- Stores data and instructions in tracks and sectors
- A track is a narrow recording band that forms a full circle on the surface of the disk.
- Sector consists of pie-shaped sections of the disk’s storage locations which break the tracks
into small arcs, typical sector stores up to 512 bytes
- There are three types ~ hard disks, floppy disks and zip disks
- Some of these disks are portable and some are not
- With respect to storage medium, portable means you can remove the medium from one
computer and carry it to another computer.

A computer is an electronic device operating under the control of instructions stored in its own
memory, that can accept data, process the data according to specified rules, produce results and store
results for future use.
Communication devices
A communication device is any hardware component that enables a computer to send (transmit) and
receive data, instructions and information to and from one or more computers.
The widely used communication device is the modem
Multiprocessing is the coordinated processing of programs by more than one computer processor.
Multiprocessing can mean the assignment of a program to one of two or more computers working in
tandem or can involve multiple computers working on the same program at the same time (in
parallel).
Multiprogramming
Software is the name given to the instructions which makes the computer work.
There are two types of software namely the systems software and the applications software.
Operating system is software which controls the computer’s own workings, organizing and
controlling the different hardware.
The operating system provides the user interface and file management facilities.
System software is responsible for controlling the allocation and usage of hardware resources such
as memory, CPU time, disk space and peripheral devices.
It is the foundation on which applications such as word processing and spreadsheets are built.
From intermediate info technology by Farrell, Chacko, Rowley.
Office automation refers to the use of integrated computer and communication systems to
support administrative procedures in an office environment.
Automation refers to controlled operation of an operation of an apparatus, process, or
system by electronic devices that take the place of human observation and effort.
E-office relates to the office where all activities and transactions are taking place
electronically rather via a paper-based system.
What is output?
• Output is data that has been processed into useful form.
• Users view output on a screen, print it, or hear it through speakers, headphones or earphones.
• While working with a computer, a user encounters four (4) basic categories of output: text,
graphics, audio and video.
Output device refers to any hardware component of a computer that conveys information to one or
more people.
-examples include display devices, printers, speakers, headphones, earphones, fax machines, fax
modems, multifunction peripheral devices and data projectors.
Data projector is a device that takes the text and images displaying on a computer screen and
projects them on a larger screen so an audience can see the image clearly.
Some data projectors are large devices that attach to a ceiling or wall in auditorium.

Scsite.comdcf3e/ch5looking/Digital cinema
Multifunction peripherals
Multifunction peripheral is a single device that looks like a copy machine but provides the
functionality of a printer, scanner, copy machine and perhaps a fax machine.
Some use colour inkjet technology while others include a black-and-white laser printer
Advantage-significantly less expensive than if you purchase each device separately
Disadvantage-if the device breaks down, however, you lose all four functions
Display devices
-display device is an output device that visually conveys text, graphics and video information.
-desktop computers typically use a monitor as their display device.
Monitor
-is a display device that is packaged as a separate peripheral
-most monitors have a tilt-and-swivel base that allows users to adjust the angle of the screen to
minimize neck strain and reduce glare from overhead lighting
-monitor controls permits users to adjust the brightness, contrast, positioning, height and width of
images
-most mobile computers and devices integrate the display and other components into the same
physical case.
Types of monitors
Teleworking describes people using computers and telecommunications to work from their own
homes rather than travelling to a central office.
Advantages
-fewer distractions for workers from their fellow employees and the company environment
-flexible schedule, that is, teleworkers have more freedom to choose the hours they work, thus
resulting in higher productivity and happier workers
-teleworker has more time with his/her family
-result reduced congestion in cities
-result reduced air pollution emanating from exhaust fumes
Disadvantages
-cost of providing technology to individual teleworkers is expensive

-the different skills needed to manage home workers may be lacking in management
-the difficulties of solving technical problems experienced by telecommuters especially those in
remote areas (kilometers away from head office) hinder its wide spread
-many homeworkers feel isolated from colleagues and alienated from the company that they are
working for

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