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EIT 4150: INTRODUCTION TO INFORMATION TECHNOLOGY
Computer Terminologies
Information: An organized, meaningful, and useful interpretation of data.
–Data
–Text
–Sound
–Images
Data: Raw facts, figures, and details.
Information Technology Professional is a person who is responsible for acquiring, developing, maintaining, or operating the hardware associated with computers and communications networks. They are:
–Programmers: write codes using programming languages to solve problems.
–Systems Analysts: work with users to determine the requirements an application must meet.
–System Designers: they formulate application specification and design the features of custom software.
–Web Designers: these are specialists who focus primarily on developing applications for the internet and the World Wide Web.
IT Procedures
A Procedure is a step-by-step process or a set of instructions for accomplishing specific results. These are: Operations, Backup and Recovery, Security, Development.
 Operations Procedure: A procedure that describes how a computer system or application is used, how often it can be used, who is authorized to use it, and where the results of processing should go.
 Backup Procedure: A procedure that describes how and when to make extra copies of information or software to protect against losses.
 Recovery Procedure: An action taken when information or software must be restored.
 Security Procedure: A procedure designed to safeguard data centres, communications networks, computers, and other IT components from accidental intrusion or intentional damage.
 Security Software: Software that is designed to protect systems and data.
 Development Procedure: A procedure that explains how IT professionals should describe user needs and develop applications to meet those needs.
Systems
A System is a set of components that interact to accomplish a purpose.
•Single-User System (Personal Computer): An IT system used by only one person. A system that stands alone and is not interconnected with other companies or shared by other people.
•Multi-user System: A communication system in which more than one user share hardware, programs, information, people, and procedures.
–To share a computer
–To share hardware
–To share software
–To share information
–To share communications
Computer System: The computer system is made up of two components parts (Hardware and Software). These components integrate and interrelate. They do this independently by
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interacting together to perform the basic operations of the computer system. These components are linked together via cords and interface connectors.
Program: A set of instructions that directs a computer to perform certain tasks and produce certain results.
Knowledge: An awareness and understanding of a set of information and how that information can be put to the best use.
Information System: A business information system designed to produce the information needed for successful management of a structured problem, process, department, or business.
Information and communication technology (ICT) is an umbrella term that covers all advanced technologies in manipulating and communicating Information.
The term is sometimes used in preference to Information Technology (IT) or "InfoTech". It is sometimes said to have been coined to modernize the outdated phrase "data processing".
Information Technology means the processing and distribution of data using computer hardware and software, telecommunications, and digital electronics.
ICT is concerned with the storage, retrieval, manipulation, transmission or receipt of digital data. Importantly, it is also concerned with the way these different uses can work with each other in business.
The nature of information (the "I" in ICT) covers areas such as the meaning and value of information; how information is controlled;
The C part of ICT refers to the communication of data by electronic means, usually over some distance. This is often achieved via networks of sending and receiving equipment, wires and satellite links.
•The T part of ICT refers to the more recent, and fast-growing range of digital technologies which allow people and organizations to communicate and share information digitally
ICT three main components are:
–Computers; used to process data into information,
–Communications networks; transmission of information,
–Know-how; the technology used for the transmission
INTRODUCTION TO COMPUTERS
Computer is an advanced electronic device that takes raw data as input from the user and processes it under the control of set of instructions (called program), gives the result (output), and saves it for the future use. Thus, a computer system is made up of two major components i.e. Hardware and software.
The term Hardware refers to the physical components that make up a computer system and a unit basically for computations and data processing operations, for example the monitor (also screen or display unit), system casement, mouse keyboard, etc
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The term Software refers to the programs which instruct the computer hardware on what to do and how to do it. Examples of software include operating systems, utility programs and the application packages.
Functionalities of a computer
Any digital computer carries out five functions in gross terms:
- Takes data as input.
- Stores the data/instructions in its memory and use them when required.
- Processes the data and converts it into useful information.
- Generates the output
- Controls all the above four steps
Advantages of using computers
i) High Speed
- Computer is a very fast device.
- It is capable of performing calculation of very large amount of data.
- The computer has units of speed in microsecond, nanosecond, and even the picosecond.
- It can perform millions of calculations in a few seconds as compared to man who will spend many months for doing the same task.
ii) Accuracy
- In addition to being very fast, computers are very accurate.
- The calculations are 100% error free.
- Computers perform all jobs with 100% accuracy provided that correct input has been given.
iii) Storage Capability
- Memory is a very important characteristic of computers.
- A computer has much more storage capacity than human beings.
- It can store large amount of data.
- It can store any type of data such as images, videos, text, audio and many others.
iv) Diligence
- Unlike human beings, a computer is free from monotony, tiredness and lack of concentration.
- It can work continuously without any error and boredom.
- It can do repeated work with same speed and accuracy.
v) Versatility
- A computer is a very versatile machine.
- A computer is very flexible in performing the jobs to be done.
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- This machine can be used to solve the problems related to various fields.
- At one instance, it may be solving a complex scientific problem and the very next moment it may be playing a card game.
vi) Reliability
- A computer is a reliable machine.
- Modern electronic components have long lives.
- Computers are designed to make maintenance easy.
vii) Automation
- Computer is an automatic machine.
- Automation means ability to perform the given task automatically.
- Once a program is given to computer i.e. stored in computer memory, the program and instruction can control the program execution without human interaction.
Disadvantages of using computers
i) No I.Q
- A computer is a machine that has no intelligence to perform any task.
- Each instruction has to be given to computer.
- A computer cannot take any decision on its own.
ii) Dependency
- It functions as per a user’s instruction, so it is fully dependent on human being.
iii) Environment
- The operating environment of computer should be dust free and suitable.
Characteristics of computers
A computer like any other machine is basically a technical creation through human engineering skills. It is necessary to establish the properties (both physical and technical) that help to identify a computer from other machines. The main characteristic features of a computer include
 Computer is versatile in that it can perform a variety of tasks
 Computer has a high processing speed because of its electronic nature
 Computer is accurate as long as the instructions given to them are correct
 Computer is capable of carrying out repetitive jobs routinely any number of times
 Computer can perform program execution automatically without human intervention
COMPUTER APPLICATION AREAS
In the modern business operations it has been found necessary to make use of computers especially to change the business image and have an advantage in the competitive business environment. Therefore Computers are presently being used in the following application areas:
i) Business
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A computer has high speed of calculation, diligence, accuracy, reliability, or versatility which made it an integrated part in all business organizations. Computer is used in business organizations for:
- Payroll calculations
- Budgeting
- Sales analysis
- Financial forecasting
- Managing employees database
- Maintenance of stocks etc.
ii) Banking
Today banking is almost totally dependent on computer. Banks provide following facilities:
- Banks provide online accounting facility, which includes current balances, deposits, overdrafts, interest charges, shares, and trustee records.
- ATM machines are making it even easier for customers to deal with banks.
iii) Education
The computer has provided a lot of facilities in the education system.
- The computer provides a tool in the education system known as CBE (Computer Based Education).
- CBE involves control, delivery, and evaluation of learning.
- The computer education is rapidly increasing the graph of number of computer students.
- It is used to prepare a database about performance of a student and analysis is carried out on this basis.
iv) Marketing
In marketing, uses of computer are following:
- Advertising - With computers, advertising professionals create art and graphics, write and revise copy, and print and disseminate ads with the goal of selling more products.
- At Home Shopping - Home shopping has been made possible through use of computerized catalogues that provide access to product information and permit direct entry of orders to be filled by the customers.
v) Health Care
Computers have become important part in hospitals, labs, and dispensaries. The computers are being used in hospitals to keep the record of patients and medicines. It is also used in scanning and diagnosing different diseases. ECG, EEG, Ultrasounds and CT Scans etc. are also done by computerized machines.
Some major fields of health care in which computers are used are:
- Diagnostic System - Computers are used to collect data and identify cause of illness.
- Lab-diagnostic System - All tests can be done and reports are prepared by computer.
- Patient Monitoring System - These are used to check patient's signs for abnormality such as in Cardiac Arrest, ECG etc.
- Pharma Information System - Computer checks Drug-Labels, Expiry dates, harmful drug’s side effects etc.
- Surgery: Nowadays, computers are also used in performing surgery.
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vi) Communication
Communication means to convey a message, an idea, a picture or speech that is received and understood clearly and correctly by the person for whom it is meant for. Some main areas in this category are:
- E-mail
- Chatting
- Video-conferencing
Types Of computers /Classification of Computers
Computers can be classified into different categories based on the following criteria:
 By the types of data which they can manipulate / process or According to Technology
 By the purpose for which they are design or By functions performed
 On the basis of price, sizes and processing capabilities
 According to Generations.
a) By the types of data which they can manipulate / process or According to Technology
- Analog Computers
- Digital Computers
- Hybrid Computers
Analog Computers:- These computers recognize data as a continuous measurement of a physical property and operates essentially by measuring rather counting. As the data is continuously variable, the results obtained are estimated and not exactly repeatable. Voltage, temperature, speed and pressure are measured using analog devices like voltmeters, thermometers, Automobile speedometer and barometers (voltage, pressure, speed and temperature).
Analog (continuous) signal
Digital Computers:- These are high speed programmable electronic devices that perform mathematical calculations, compare values and store results. They recognize data by counting discrete signal representing either a high or low or ‘on’ or ‘off’ voltage state of electricity. Therefore, the results obtained from a digital computer are measurable and precise. Virtually all of today's computers are based on digital principles.
Digital (discrete) signals
Hybrid Computers:- Hybrid computers accept data in analog form and present output also in analog form. The data, however, is processed digitally. Therefore, hybrid computers require analog-to-digital converters for input and digital-to-analog converters for output. Also we can say that hybrid computers are computers that process both
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analog and digital data.
b) By the purpose for which they are designed or by functions performed
Special Purpose Computers
A special purpose computer is designed to solve a single type of problem. The functions are uniquely adapted to a particular situation. Therefore, within their designed constraints, they are extremely fast, efficient and economical. Computerized traffic control system and
automatic aircraft landing systems are examples of special purpose computer systems.
General Purpose Computers
General purpose computers are designed to be flexible and versatile. They are capable of carrying out some general data processing under program control. They can be used to solve a variety of problems by changing the program or instructions which govern their operations. A ‘General Purpose Computer’ therefore refers to computers that follow instructions, thus virtually all computers from micro to mainframe are general purpose. Even computers in toys, games and single-function devices follow instructions in their built-in program.
c) On the basis of price, sizes and processing capabilities
- Supercomputers
- Mainframe Computers
- Minicomputers
- Microcomputers
- Portable computers
SUPERCOMPUTERS
 Supercomputers are one of the biggest and fastest computers currently available. Supercomputers are very expensive and are employed for specialized applications that require immense amount of mathematical calculations (number crunching). For example, weather forecasting, scientific simulations, (animated) graphics, fluid dynamic calculations, nuclear energy research, electronic design, and analysis of geological data (e.g. in petrochemical prospecting).
 Because of their size and expense, supercomputers are relatively rare.
MAINFRAMES COMPUTERS
 Much smaller than supercomputers
 Mainframe is very large in size and is an expensive computer capable of supporting hundreds or even thousands of users simultaneously.
 Mainframe executes many programs concurrently and supports many simultaneous executions of programs.
 Used for handling bulk data and information processing of large organizations e.g. banks, hospitals, railways, airports etc
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 Used in environments where users shares common computing needs e.g. research groups, educational institutions, engineering firms, etc
A typical configuration for a mainframe consists of the following components
 Host computers – carries out most of the computations and controls over all other computers
 Front-end computers - used for handling communications to and from all the user terminals connected to the system computer
 Back – end computers – used to handle data I/O operations thus relieving host computer of locating particular I/O device and transferring of data
 Console(s) – terminals connected directly and used by system administrators to monitor the operations and configuration of the main system
 Storage devices – have several drives connected to the back end for back up and restoration
 User terminals – act as access points for users to simultaneously use the system through multiprogramming, multitasking and timesharing
 Output devices – resources that are accessible by the users for taking their outputs
MINICOMPUTERS
 Minicomputers: are smaller than mainframe, general purpose computers, and give computing power without adding the prohibitive expenses associated with larger systems. It is generally easier to use.
 They are midsize multi-processing systems capable of supporting up to 250 users simultaneously.
 Minicomputers usually have multiple terminals.
 Minicomputers may be used as network servers and Internet servers.
Microcomputers
 Is the smallest, least expensive of all the computers and designed to be used by one person at a time i.e. single – user computers.
 They are typically linked together to form a local-area network, although they can also be used as stand-alone systems.
 Micro computers have smallest memory and less power, are physically smaller and permit fewer peripherals to be attached.
 Microcomputers are more commonly known as desktop or sometimes workstation.
Portable computers
Portable computers are computers that are designed to be carried around easily, such as in a briefcase or in a pocket. Under these we have:
 Notebook(Laptop)
Computers that are about the size of a paper notebook and open to reveal a screen on the top half of the computer and a keyboard at the bottom.
 Tablet Computers
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These are notebook sized designed to be used with a digital pen or a stylus. They can either be slate tablets or convertible tablets.
 Net books
Also called mini laptops, mini notebooks. They are smaller with about a 10 inch screen, are lighter and less expensive than common laptops.
 Ultra-mobile PC’s
Also known as UMPCs or handheld computers. These are computers that are small enough to fit in one hand. They have a screen of 7 inches or smaller.
d) According to Generations
Generation in computer terminology is a change in technology a computer is/was being used. Initially, the generation term was used to distinguish between varying hardware technologies. But nowadays, generation includes both hardware and software, which together make up an entire computer system.
There are totally five computer generations known till date. Each generation has been discussed in detail along with their time period and characteristics. Here approximate dates against each generations have been mentioned which are normally accepted.
First Generation (1946-1959)
The computers of first generation used vacuum tubes as the basic components for memory and circuitry for CPU (Central Processing Unit). These tubes, like electric bulbs, produced a lot of heat and were prone to frequent fusing of the installations, therefore, were very expensive and could be afforded only by very large organizations. In this generation mainly batch processing operating system were used. Punched cards, paper tape, and magnetic tape were used as input and output devices. The computers in this generation used machine code as programming language.
The main features of first generation are:
- Vacuum tube technology
- Unreliable
- Supported machine language only
- Very costly
- Generated lot of heat
- Slow input and output devices
- Huge size
- Need of A.C.
- Non-portable
- Consumed lot of electricity
Some computers of this generation were:
- Electronic Numerical Integrator And Computer (ENIAC)
- Electronic Discrete Variable Automatic Computer (EDVAC)
- (UNIVersal Automatic Computer) UNIVAC
- (International Business Machines) IBM-701
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- IBM-650
Second Generation (1959-1965)
In this generation transistors were used that were cheaper, consumed less power, more compact in size, more reliable and faster than the first generation machines made of vacuum tubes. In this generation, magnetic cores were used as primary memory and magnetic tape and magnetic disks as secondary storage devices. In this generation assembly language and high-level programming languages like FORTRAN, COBOL were used. The computers used batch processing and multiprogramming operating system.
The main features of second generation are:
- Use of transistors
- Reliable in comparison to first generation computers
- Smaller size as compared to first generation computers
- Generated less heat as compared to first generation computers
- Consumed less electricity as compared to first generation computers
- Faster than first generation computers
- Still very costly
- A.C. needed
- Supported machine and assembly languages
Some computers of this generation were:
- IBM 1620
- IBM 7094
- CDC 1604
- CDC 3600
- UNIVAC 1108
Third Generation (1965-1971)
The computers of third generation used integrated circuits (IC's) in place of transistors. A single IC has many transistors, resistors and capacitors along with the associated circuitry. The IC was invented by Jack Kilby. This development made computers smaller in size, reliable and efficient. In this generation remote processing, time-sharing, multi-programming operating system were used. High-level languages (FORTRAN-II TO IV, COBOL, PASCAL PL/1, BASIC, ALGOL-68 etc.) were used during this generation.
The main features of third generation are:
- IC used
- More reliable in comparison to previous two generations
- Smaller size
- Generated less heat
- Faster
- Lesser maintenance
- Still costly
- A.C needed
- Consumed lesser electricity
- Supported high-level language
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Some computers of this generation were:
- IBM-360 series
- Honeywell-6000 series
- PDP(Personal Data Processor)
- IBM-370/168
Fourth Generation (1971-1980)
The computers of fourth generation used Very Large Scale Integrated (VLSI) circuits. VLSI circuits having about 5000 transistors and other circuit elements and their associated circuits on a single chip made it possible to have microcomputers of fourth generation. Fourth generation computers became more powerful, compact, reliable, and affordable. As a result, it gave rise to personal computer (PC) revolution. In this generation time sharing, real time, networks, distributed operating system were used. All the high-level languages like C, C++, DBASE etc. were used in this generation.
The main features of fourth generation are:
- VLSI technology used
- Very cheap
- Portable and reliable
- Use of PC's
- Very small size
- Pipeline processing
- No A.C. needed
- Concept of internet was introduced
- Great developments in the fields of networks
- Computers became easily available
Some computers of this generation were:
- STAR 1000
- CRAY-1(Super Computer)
- CRAY-X-MP(Super Computer)
Fifth Generation (1980 – date)
In the fifth generation, the VLSI technology became ULSI (Ultra Large Scale Integration) technology, resulting in the production of microprocessor chips having ten million electronic components. This generation is based on parallel processing hardware and AI (Artificial Intelligence) software. AI is an emerging branch in computer science, which interprets means and method of making computers think like human beings. All the high-level languages like C and C++, Java, .Net etc. are used in this generation.
AI includes:
- Robotics
- Neural networks
- Game Playing
- Development of expert systems to make decisions in real life situations.
- Natural language understanding and generation.
The main features of fifth generation are:
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- ULSI technology
- Development of true artificial intelligence
- Development of Natural language processing
- Advancement in Parallel Processing
- Advancement in Superconductor technology
- More user friendly interfaces with multimedia features
- Availability of very powerful and compact computers at cheaper rates
Some computer types of this generation are:
- Desktop
- Laptop
- NoteBook
- UltraBook
- ChromeBook
Hardware components of a computer system
A computer system can be categorized into six major components as shown below.
The central processing unit (CPU) manipulates data and controls the other parts of the computer system; primary storage temporarily stores data and program instructions during processing; secondary storage stores data and instructions when they are not used in processing; input devices convert data and instructions for processing in the computer; output devices present data in a form that people can understand; and communications devices control the passing of information to and from communications networks.
Secondary storage devices such as floppy disks, optical disks, and hard disks are used to store large quantities of data outside the CPU and primary storage. They provide direct access to data for easy retrieval.
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The CPU is connected to the rest of the system through system bus. Through system bus, data or information gets transferred between the CPU and the other component of the system. The system bus may have three components:
- Data Bus: Data bus is used to transfer the data between main memory and CPU.
- Address Bus: Address bus is used to access a particular memory location by putting the address of the memory location.
- Control Bus: Control bus is used to provide the different control signal generated by CPU to different part of the system. As for example, memory read is a signal generated by CPU to indicate that a memory read operation has to be performed. Through control bus this signal is transferred to memory module to indicate the required operation
Central Processing Unit (CPU)
 CPU is considered as the brain of the computer
 The operations or tasks that must perform by CPU are:
- Fetch Instruction: The CPU reads an instruction from memory.
- Interpret Instruction: The instruction is decoded to determine what action is required.
- Fetch Data: The execution of an instruction may require reading data from memory or I/O module.
- Process data: The execution of an instruction may require performing some arithmetic or logical operation on data.
- Write data: The result of an execution may require writing data to memory or an I/O module.
To do these tasks, it should be clear that the CPU needs to store some data temporarily. It must remember the location of the last instruction so that it can know where to get the next instruction. It needs to store instructions and data temporarily while an instruction is being executed. In other words, the CPU needs a small internal memory. These storage locations are generally referred as registers.
CPU itself has following three components.
 Memory Or Storage Unit:
 Control Unit
 ALU(Arithmetic Logic Unit)
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Control Unit
This unit controls the operations of all parts of computer. It does not carry out any actual data processing operations.
Functions of this unit are
 It is responsible for controlling the transfer of data and instructions among other units of a computer.
 It manages and coordinates all the units of the computer.
 It obtains the instructions from the memory, interprets them and directs the operation of the computer.
 It communicates with Input / Output devices for transfer of data or results from storage.
 It does not process or store data.
Arithmetic Logic Unit (ALU)
This unit consists of two sub section namely
 Arithmetic section
 Logic Section
Arithmetic section
Function of Arithmetic section is to perform arithmetic operations like addition, subtraction, multiplication and division. All complex operations are done by making repetitive use of above operations.
Logic Section
Function of logic section is to perform logic operations such as comparing, selecting, matching and merging of data.
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Memory and storage
A memory is just like a human brain. It is used to store data and instruction. Computer memory is the storage space in computer where data is to be processed and instructions required for processing are stored.
Its size affects speed, power and capability. There are two types of memories in the computer (primary memory and secondary memory). Functions of Memory Unit are:
 It stores all the data to be processed and the instructions required for processing.
 It stores intermediate results of processing.
 It stores final results of processing before these results are released to an output device
The memory is divided into large number of small parts. Each part is called cell. Each location or cell has a unique address which varies from zero to memory size minus one.
For example if computer has 64k words, then this memory unit has 64 * 1024=65536 memory location. The address of these locations varies from 0 to 65535.
Memory is primarily of four types
 Register
 Cache Memory
 Primary Memory/Main Memory
 Secondary Memory
Register
This is a part of Central Processor Unit, so they reside inside the CPU. The information from main memory is brought to CPU and keep the information in register. Due to space and cost constraints, we have got a limited number of registers in a CPU. These are basically faster devices.
Cache Memory
Cache memory is a very high speed semiconductor memory which can speed up CPU. It acts as a buffer between the CPU and main memory.
It is used to hold those parts of data and program which are most frequently used by CPU. The parts of data and programs are transferred from disk to cache memory by operating system, from where CPU can access them.
Advantage
 Cache memory is faster than main memory.
 It consumes less access time as compared to main memory.
 It stores the program that can be executed within a short period of time.
 It stores data for temporary use.
Disadvantage:
 Cache memory has limited capacity.
 It is very expensive.
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Primary Memory (Main Memory)
Primary memory holds only those data and instructions on which computer is currently working. It has limited capacity and data get lost when power is switched off.
It is generally made up of semiconductor device. These memories are not as fast as registers. The data and instruction required to be processed earlier reside in main memory. It is divided into two subcategories RAM and ROM.
Computer – RAM
- A RAM stands for random access memory.
- It constitutes 70% the internal memory of the CPU for storing data, program and program result.
- It is read/write memory.
- Since access time in RAM is independent of the address to the word that is, each storage location inside the memory is as easy to reach as other location & takes the same amount of time. We can reach into the memory at random & extremely fast but can also be quite expensive.
- RAM is volatile, i.e. data stored in it is lost when we switch off the computer or if there is a power failure. Hence a backup uninterruptible power system (UPS) is often used with computers.
- RAM is small, both in terms of its physical size and in the amount of data it can hold.
Computer – ROM
- ROM stands for Read Only Memory. The memory from which we can only read but cannot write on it once information is written i.e. it cannot be over written.
- It constitutes 30% the internal memory.
- This type of memory is non-volatile. The information is stored permanently in such memories during manufacture.
- It stores instructions that are required to start computer when electricity is first turned on, this operation is referred to as bootstrap.
- ROM chip are not only used in the computer but also in other electronic items like washing machine and microwave oven.
Several types of ROM are available:
PROM: Programmable Read Only Memory - is read-only memory that can be modified only once by a user. The user buys a blank PROM and enters the desired contents using a PROM program. Inside the PROM chip there are small fuses which are burnt open during programming. It can be programmed only once and is not erasable.
EPROM: Erasable Programmable Read Only Memory - the contents of the memory can be erased and store new data into the memory. In this case, we have to erase whole information.
EEPROM: Electrically Erasable and Programmable Read Only Memory - is programmed and erased electrically. It can be erased and reprogrammed about ten thousand times. Both erasing and programming take about 4 to 10 ms (milli second). In EEPROM, any location can be
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selectively erased and programmed. EEPROMs can be erased one byte at a time, rather than erasing the entire chip. Hence, the process of re-programming is flexible but slow.
Characteristic of Primary memory (Main Memory)
- These are semiconductor memories.
- It known as main memory.
- Usually volatile memory.
- Data is lost in case power is switch off.
- It is working memory of the computer.
- Faster than secondary memories.
- A computer cannot run without primary memory.
Secondary Memory
- This type of memory is also known as backing storages or auxiliary storages.
- They refer to computer storage which offers permanent storage of data and programs that are not currently being executed by the computer.
- Backing storages can be said to supplement the main memory because they offer non-volatile storage as well as more capacity for data storage, thus overcoming the limitation of storage capacity and volatility of main memory.
- However secondary memories are slower than main memory.
- For example: disk, CD-ROM, DVD etc.
The secondary storage in a computer is therefore necessary for the following reasons:
- most primary storage is semi-conductor memory, and the data are lost when electricity is interrupted
- To supplement main memory because of its limited capacity
- Main memory is very expensive and therefore it can be used for storing the necessary instructions and data currently being operated on.
- For easier transportation (transfer purposes)
- Security purposes (data is not accessible to all people)
- For back up purposes in case of hard ware corruption
- ROM stores data permanently. Cannot update data once stored. Need for a storage where updating can be done.
- For exchanging programs and data, including vending of software
Characteristic of Secondary Memory
- These are magnetic and optical memories.
- It is known as backup memory.
- It is non-volatile memory.
- Data is permanently stored even if power is switched off.
- It is used for storage of the data in the computer.
- Computer may run without secondary memory.
- Slower than primary memories.
Computer - Memory Units
- It is the amount of data that can be stored in the storage unit.
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- The storage capacity is expressed in terms of Bytes.
Following are the main memory storage units:
- Bit (Binary Digit): A binary digit is logical 0 & 1 representing a passive or an active state of a component in an electric circuit.
- Nibble : A group of 4 bits is called nibble.
- Byte : A group of 8 bits is called byte. A byte is the smallest unit which can represent a data item or a character.
- Word : A computer word like a byte, is a group of fixed number of bits processed as a unit which varies from computer but is fixed for each computer. The length of a computer word is called word-size or word length and it may be as small as 8 bits or may be as long as 96 bits. A computer stores the information in the form of the computer words.
Few higher storage units are as follows:
- Kilobyte (KB) : 1 KB = 1024 Bytes
- Megabyte (MB) : 1 MB = 1024 KB
- GigaByte (GB) : 1 GB = 1024 MB
- TeraByte (TB) : 1 TB = 1024 GB
- PetaByte (PB) : 1 PB = 1024 TB
Computer - Input Devices
Following are few of the important input devices which are used in Computer Systems
 Keyboard
 Mouse
 Joy Stick
 Light pen
 Track Ball
 Scanner
 Graphic Tablet
 Microphone
 Magnetic Ink Card Reader(MICR)
 Optical Character Reader(OCR)
 Bar Code Reader
 Optical Mark Reader
Mouse
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Mouse is most popular Pointing device. It is a very famous cursor-control device. It is a small palm size box with a round ball at its base which senses the movement of mouse and sends corresponding signals to CPU on pressing the buttons.
Generally it has two buttons called left and right button and scroll bar is present at the mid. Mouse can be used to control the position of cursor on screen, but it cannot be used to enter text into the computer.
Advantages
 Easy to use
 Not very expensive
 Moves the cursor faster than the arrow keys of keyboard.
Keyboard
Most common and very popular input device is keyboard. The keyboard helps in inputting the data to the computer. The layout of the keyboard is like that of traditional typewriter, although there are some additional keys provided for performing some additional functions.
The following are categories of keys:
No.
Keys
Description
1
Typing Keys / Alphanumeric keys
These keys include the letter keys (A-Z) and digits keys (0-9) which are generally give same layout as that of typewriters.
2
Numeric Keypad
It is used to enter numeric data or cursor movement. Generally, it consists of a set of 17 keys that are laid out in the same configuration used by most adding machine and calculators.
3
Function Keys
The twelve functions keys are present on the keyboard. These are arranged in a row along the top of the keyboard. Each function key has unique meaning and is used for some specific purpose.
4
Control keys
These keys provides cursor and screen control. It includes four directional arrow key. Control keys also include Home, End, Insert, Delete, Page Up, Page Down,
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Control(Ctrl), Alternate(Alt), Escape(Esc).
5
Special Purpose Keys
Keyboard also contains some special purpose keys such as Enter, Shift, Caps Lock, Num Lock, Space bar, Tab, and Print Screen.
Joystick
Joystick is also a pointing device which is used to move cursor position on a monitor screen.
It is a stick having a spherical ball at its both lower and upper ends. The lower spherical ball moves in a socket. The Joystick can be moved in all four directions.
The function of joystick is similar to that of a mouse. It is mainly used in Computer Aided Designing (CAD) and playing computer games.
Light Pen
Light pen is a pointing device which is similar to a pen. It is used to select a displayed menu item or draw pictures on the monitor screen. It consists of a photocell and an optical system placed in a small tube.
When light pen's tip is moved over the monitor screen and pen button is pressed, its photocell sensing element detects the screen location and sends the corresponding signal to the CPU.
Track Ball
Track ball is an input device that is mostly used in notebook or laptop computer, instead of a mouse. This is a ball which is half inserted and by moving fingers on ball, pointer can be moved.
Since the whole device is not moved, a track ball requires less space than a mouse. A track ball comes in various shapes like a ball, a button and a square.
Scanner
Scanner is an input device which works more like a photocopy machine. It is used when some information is available on a paper and it is to be transferred to the hard disc of the computer
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for further manipulation.
Scanner captures images from the source which are then converted into the digital form that can be stored on the disc. These images can be edited before they are printed.
Digitizer
Digitizer is an input device which converts analog information into a digital form. Digitizer can convert a signal from the television camera into a series of numbers that could be stored in a computer. They can be used by the computer to create a picture of whatever the camera had been pointed at.
Digitizer is also known as Tablet or Graphics Tablet because it converts graphics and pictorial data into binary inputs. A graphic tablet as digitizer is used for doing fine works of drawing and images manipulation applications.
Microphone
Microphone is an input device to input sound that is then stored in digital form. The microphone is used for various applications like adding sound to a multimedia presentation or for mixing music.
Magnetic Ink Card Reader (MICR)
MICR input device is generally used in banks because of a large number of cheques to be processed every day. The bank's code number and cheque number are printed on the cheques with a special type of ink that contains particles of magnetic material that are machine readable.
This reading process is called Magnetic Ink Character Recognition (MICR). The main advantage of MICR is that it is fast and less error prone.
Optical Character Reader (OCR)
OCR is an input device used to read a printed text. OCR scans text optically character by character, converts them into a machine readable code and stores the text on the system memory.
Bar Code Readers
Bar Code Reader is a device used for reading bar coded data (data in form of light and dark lines). Bar coded data is generally used in labelling goods, numbering the books etc. It may be a hand held scanner or may be embedded in a stationary scanner.
Bar Code Reader scans a bar code image, converts it into an alphanumeric value which is then fed to the computer to which bar code reader is connected.
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Optical Mark Reader (OMR)
OMR is a special type of optical scanner used to recognize the type of mark made by pen or pencil. It is used where one out of a few alternatives is to be selected and marked. It is specially used for checking the answer sheets of examinations having multiple choice questions.
Computer - Output Devices
Printers
Printer is the most important output device, which is used to print information on paper.
There are two types of printers
 Impact Printers
 Non-Impact Printers
Impact Printers
The printers that print the characters by striking against the ribbon and onto the paper, are called impact printers.
Characteristics of Impact Printers are following
 Very low consumable costs
 Impact printers are very noisy
 Useful for bulk printing due to low cost
 There is physical contact with the paper to produce an image
These printers are of two types
 Character printers
 Line printers
Character Printers:
Character Printers are printers which print one character at a time.
These are of further two types
 Dot Matrix Printer(DMP)
 Daisy Wheel
Dot Matrix Printer
In the market one of the most popular printer is Dot Matrix Printer because of their ease of printing features and economical price. Each character printed is in form of pattern of Dot's
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and head consists of a Matrix of Pins of size (5*7, 7*9, 9*7 or 9*9) which comes out to form a character that is why it is called Dot Matrix Printer.
Advantages
 Inexpensive
 Widely Used
 Other language characters can be printed
Disadvantages
 Slow Speed
 Poor Quality
Daisy Wheel
Head is lying on a wheel and Pins corresponding to characters are like petals of Daisy (flower name) that is why it is called Daisy Wheel Printer.
These printers are generally used for word-processing in offices which require a few letters to be sent here and there with very nice quality representation.
Advantages
 More reliable than DMP's
 Better quality
 The fonts of character can be easily changed.
Disadvantages
 Slower than DMP's
 Noisy
 More expensive than DMP's
Line Printers
Line printers are printers which print one line at a time.
These are of further two types
 Drum Printer
 Chain Printer
Drum Printer
This printer is like a drum in shape so it called drum printer. The surface of drum is divided into number of tracks. Total tracks are equal to size of paper i.e. for a paper width of 132 characters, Drum will have 132 tracks. A character set is embossed on track. The different characters sets are available in market 48 character set, 64 and 96 characters set.One rotation of drum prints one line. Drum Printers are fast in speed and speed in between 300 to 2000 lines per minute.
Advantages
 Very high speed
Disadvantages
 Very expensive
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 Characters fonts cannot be changed
Chain Printer
In this printer chain of character sets are used so it called Chain Printers. A standard character set may have 48, 64, 96 characters.
Advantages
 Character fonts can easily be changed.
 Different languages can be used with the same printer.
Disadvantages
 Noisy
 Do not have the ability to print any shape of characters.
Non-impact Printers
The printers that print the characters without striking against the ribbon and onto the paper, are called Non-impact Printers. These printers print a complete page at a time, also called as Page Printers.
These printers are of two types
 Laser Printers
 Inkjet Printers
Characteristics of Non-impact Printers
 Faster than impact printers.
 They are not noisy.
 High quality.
 Support many fonts and different character size.
Laser Printers
These are non-impact page printers. They use laser lights to produces the dots needed to form the characters to be printed on a page.
Advantages
 Very high speed.
 Very high quality output.
 Give good graphics quality.
 Support many fonts and different character size.
Disadvantage
 Expensive.
 Cannot be used to produce multiple copies of a document in a single printing.
Inkjet Printers
Inkjet printers are non-impact character printers based on a relatively new technology. They print characters by spraying small drops of ink onto paper. Inkjet printers produce high quality
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Computer – Ports
 A computer port is a physical docking point using which an external device can be connected to the computer.
 A computer port can also be programmatic docking point through which information flows from a program to computer or over the internet.
Characteristics
 External devices are connected to a computer using cables and ports.
 Ports are slots on the motherboard into which a cable of external device is plugged in.
 Examples of external devices attached via ports are mouse, keyboard, monitor, microphone, speakers etc.
output with presentable features.
They make less noise because no hammering is done and these have many styles of printing modes available. Colour printing is also possible. Some models of Inkjet printers can produce multiple copies of printing also.
Advantages
 High quality printing
 More reliable
Disadvantages
 Expensive as cost per page is high
 Slow as compare to laser printer
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The following are few important types of ports:
Serial Port
 Used for external modems and older computer mouse.
 Two versions: 9 pin, 25 pin model.
 Data travels at 115 kilobits per second.
Parallel Port
 Used for scanners and printers
 Also called printer port.
 25 pin model.
 Also known as IEEE 1284-compliant Centronics port.
PS/2 Port
 Used for old computer keyboard and mouse
 Also called mouse port.
 Most of the old computers provide two PS/2 port, each for mouse and keyboard.
 Also known as IEEE 1284-compliant Centronics port.
Universal Serial Bus (or USB) Port
 Can connect all kind of external USB devices such as external hard disk, printer, scanner, mouse, keyboard etc.
 Introduced in 1997.
 Most of the computers provide two USB port as minimum.
 Data travels at 12 megabits per seconds
 USB compliant devices can get power from a USB port
VGA Port
 Connects monitor to a computer's video card.
 Has 15 holes.
 Similar to serial port connector but serial port connector has pins, it has holes.
Power Connector
 Three-pronged plug
 Connects to the computer's power cable that plugs into a power bar or wall socket.
Firewire Port
 Transfer large amounts of data at very fast speed.
 Connects camcorders and video equipments to the computer
 Data travels at 400 to 800 megabits per seconds
 Invented by Apple
 Three variants: 4-Pin FireWire 400 connector, 6-Pin FireWire 400 connector and 9-Pin FireWire 800 connector
Modem
 Connects a PC's modem to the telephone network.
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Ethernet Port
 Connects to a network and high speed Internet
 Connect network cable to a computer.
 This port resides on an Ethernet Card.
 Data travels at 10 megabits to 1000 megabits per seconds depending upon the network bandwidth.
Game Port
 Connect a PC to a joystick
 Now replaced by USB.
Digital Video Interface , DVI port
 Connect a Flat panel LCD monitors to the computer's high end video graphic cards.
 Very popular among video card manufacturers.
Sockets
 Connect microphone, speakers to sound card of the computer
Computer Specification
When buying a desktop computer one of the first things to look at will be its use and individual budget. For example, a machine that will be primarily used for gaming should focus on lots of memory, a powerful processor, enhanced video and graphics, while a computer that will be used for Internet browsing and simple word processing will not need all these. This computer‐ buying guide covers the basics idea of the important features to look at.
Speed
The processor speed is measured in Gigahertz (GHz). There are budget processors, mid grade and high‐ end processors. The high end ones maybe necessary for enhanced computer functions, such as gaming and entertainment, but overall the mid grade types are quite good and will deliver great performance for most uses. Overall the best brand name for processors is Intel.
Memory
Memory is used to run programs on the computer and the more RAM you have the better the performance and speed of computing and to avoid slowdowns and crashes. Gaming and entertainment need a lot more memory than regular computer tasks for which 1GB is usually sufficient, but 2GB is really great. At least 3GB is optimal for gaming and media experiences. Also, it is a good idea to check and make sure that there are open memory upgrade sl ots so you can always add more memory as it is fairly cheap and easy to install.
Hard Drives
Hard drives are significant for the speed capacity of computers. Overall, the larger the drive the more storage space and the faster the computer. Optimal is 500GB.
Optical Drives ‐ CD/DVD
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Most computers these days come with DVD/CD burners, and even if they do not they are cheap and easy to install and come in internal and external versions.
External Ports and Connections
Ports are used to attach peripherals, such as printers, Internet, iPods and others. Overall, the more ports you have the more variety and options will be available to add ons.
Monitors
A good monitor is essential for a quality computer experience. The older cathode ray tube (CRT) model s have become largely obsolete with the introduction of the liquid crystal display (LCD) screen monitor, however many people still use them and they can still be found at online shopping sites. LCD screen monitors have a superior display with a reduced size due to the flat panel and their lower power consumption over the CRT models. They come in a variety of sizes and sometimes the larger ones are a better value for the money and make the best experience for gaming, entertainment, such as video watching and are much easier on the eyes.
Computer Softwares
Software is a term used to describe programs and associated documentations. Software enables computer hardware to operate effectively. It instructs computers on what to do and how to do it.
Software is a set of instructions that cause a computer to perform one or more tasks. The set of instructions is often called a program. Computers cannot do any useful work without instructions from software; thus a combination of software and hardware (the computer) is necessary to do any computerized work.
A program must tell the computer each of a set of tasks to perform, in a framework of logic, such that the computer knows exactly what to do and when to do it.
Classification of software
Software can be broadly classified into system software and application software
Software
Application Software
System Software
Tailor made Applications
Readymade Applications
Operating System
Utilities Programs
Programming languages
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System Software
They consist of programs that control operations of the computer and enable user to make efficient use of computers. They coordinate computer activities and optimize use of computers. They are used to control the computer and develop and run application programs. Examples of jobs done by the system software are management of computer resources, defragmentation etc.
System softwares are further divided into operating systems and utilities softwares.
 Operating system – is a complex and most important program that runs on a computer and
which controls the operation of a computer. It perform basic tasks, such as recognizing input from the keyboard, sending output to the display screen, keeping track of files and directories on the disk, and controlling peripheral devices such as disk drives and printers.
In general the operating system supervises and directs all the software components and the hardware components. It minimizes the amount of human intervention required during processing. It also helps application programs perform common operations such as accessing a network, entering data, saving and retrieving files, and printing or displaying output. Examples of computers operating systems are UNIX, Microsoft windows 95/98, Windows 2000, Windows XP, Windows Vista and Linux.
Functions of an Operating System: The basic functions of an operating system include a user interface, resource management, task management, file management, and utilities and other functions.
- Booting the computer: This is the process of starting or restarting the computer. A cold boot is when you turn on the computer that has been turned off completely.
- The User Interface. The user interface is the part of the operating system that allows you to communicate with it so you can load programs, access files, and accomplish other tasks. Three main types of user interfaces are the command-driven, menu-driven, and graphical user interfaces. The trend in user interfaces for operating systems and other software is moving away from the entry of brief end user commands, or even the selection of choices from menus of options. Instead, the trend is toward an easy-to-use graphical user interface (GUI) that uses icons, bars, buttons, boxes, and other images. GUIs rely on pointing devices like the electronic mouse or trackball to make selections that help you get things done.
- Resource Management An operating system uses a variety of resource management programs to manage the hardware and networking resources of a computer system, including its CPU, memory, secondary storage devices, telecommunications processors, and input/output peripherals. For example memory management programs keep track of where data and programs are stored. They may also subdivide memory into a number of sections and swap parts of programs and data between memory and magnetic disks or other secondary storage devices. This can provide a computer system with a virtual memory capability that is significantly larger than the real memory capacity of its primary
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storage unit. So, a computer with a virtual memory capability can process larger programs and greater amounts of data than the capacity of its memory circuits would normally allow.
- File Management An operating system contains file management programs that control the creation, deletion, and access of files of data and programs. File management also involves keeping track of the physical location of files on magnetic disks and other secondary storage devices. So operating systems maintain directories of information about the location and characteristics of files stored on a computer system’s secondary storage devices.
- Task Management The task management programs of an operating system manage the accomplishment of the computing tasks of end users. They give each task a slice of a CPU’s time and interrupt the CPU operations to substitute other tasks. Task management may involve a multitasking capability where several computing tasks can occur at the same time. Multitasking may take the form of multiprogramming, where the CPU can process the tasks of several programs at the same time, or time-sharing, where the computing tasks of several users can be processed at the same time. The efficiency of multitasking operations depends on the processing power of a CPU and the virtual memory and multi-tasking capabilities of the operating system it uses.
 Utilities programs - Performs a variety of tasks that maintain or enhance the computers
Operating system. Each type has a specific job to do. Below are some descriptions of utilities.
- Anti-virus applications protect your computer from the damage that can be caused by viruses and similar programs
- Compression utilities make files smaller for storage (or sending over the Internet) and then return them to normal size.
- Data recovery utilities attempt to restore data and files that have been damaged or accidentally deleted.
- Firewalls prevent outsiders from accessing your computer over a network such as the Internet.
Application softwares
These are programs for user to do their jobs e.g. typing, recording keeping, production of financial statements, drawing etc.
 Readymade software - developed to perform a variety of tasks, usually determined by use.
Such software can be customized by user to achieve specific goals e.g. ms office which is a suit of programs performing a variety of tasks e.g. word processing for producing documents, database for storing, retrieving and manipulating data and spreadsheets for various accounting calculations.
NB: Nowadays most of the general purpose software is being sold as a complete software suite (Application packages) such as Microsoft office – which includes ms word, ms excel (spreadsheet), ms access, ms power point etc. These suites offer more software products packaged together at a much lower price than buying the packages separately. The following are advantages of using application packages:
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- Handling of voluminous work – Tasks that are voluminous can easily be handled by these applications with a lot of precision.
- Accuracy and Precision – Data that has to be validated must always meet the validation criteria. This enforces permanent correctness of data being processed.
- Repetitiveness – Neither the package nor the hardware will be bored or tired of doing the same task always. The same tasks will always be repeated with the same precision again and again.
- Faster Computations – a solution to a complex problem can be developed and implemented by an application package. There will be no need to spend time thinking of how the problem will be solved.
- Speed on Performance – Application packages enhance the computation speed provided by the hardware.
- Sharing of data – Application packages facilitate sharing of data in applications that are set up to cater for shared computing.
Disadvantages of using application packages
- They might not fit well into the organizations processing tanks since they are intended to meet a variety of user’s needs.
- The user may not be free to correct any routines of the package; because there is always a maintenance guarantee and/or the developer’s copyright (user doesn’t own the program only buys the right to use)
 Tailor made software: refers to computer application developed by in-house IT personnel or
outside software house according to specific user requirements in a firm. They are developed for given purpose e.g. Payroll system, stock control system etc.
Programming Languages: There are three types of programming languages.
1. Machine Languages: Computers respond only to machine language. This language is in terms of binary codes (0,1). i.e. all programs should be written with these codes, which is difficult, time consuming and leading to errors while writing the programs. There is no unique standard machine language. Rather there are many machine languages. These are machine dependent. These are referred as the first generation languages.
2. Assembly Languages: It uses mnemonic codes rather than numeric codes (as in machine languages). Ex. Add or A is used as a symbol for addition. It requires translators to convert into machine language. Like machine language, writing program in assembly language is also time consuming. These are also machine dependent.
3. High Level Languages (HLL): These are referred as problem oriented languages (POL). These are referred as third generation languages. The advantages of these languages include:
- The high level languages are convenient for writing programs as they can be written without
any codes. These languages follow rules like ―English‖ language.
- Because of their English like nature, less time is required to write a program.
- They are machine independent. A program written in any HLL can be run on computers of different types without any modifications.
SOFTWARE EVALUATION CRITERIA
The type of business operations or transaction and the Information contents are important factors in determining the nature of software application. Factors influencing choice of software includes:
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- User requirements: the selected software or package should fit user requirement as closely as possible
- Processing time: these involves the response time e.g. if the response time is slow the user might consider the software or package as unsuccessful
- Documentation: the software should be accompanied by manual, which is easy to understand by non-technical person. The manual should not contain technical jargon.
- User friendliness: the package should be easier to use with clear on screen prompts, menu driven and extensive on screen help facility
- Controls: the software should have in-built controls which may include password options, validation checks, audit trails or trace facilities etc
- Up-to-date: the software should be up-to-date e.g. should have changes or corrections in line with business procedures
- Modification: one should consider whether the user could freely change the software without violating copyright.
- Success in the market: one should consider how many users are using the software and how long it has been in the market
- Compatibility of the software: how the software integrates with other software particularly the operating system and the user programs
- Portability: one should consider how the software runs on the user computer and whether there will be need for the user to upgrade his hardware
- Cost: the user company should consider its financial position to establish whether it can afford the software required for efficient operations rather than the least cost package software available.
Computer Viruses
A set of computer instructions deliberately created that propagates and does unwanted things.
Characteristics of Computer Viruses:
- Cannot exist in a viable form, apart from another (usually legitimate) program.
- Propagates when the host program is executed.
- Has an incubation period, during which no damage is done.
- After incubation period, begins to manifest its behavior.
Sources of computer viruses
- Contact with contaminated system e.g. using contaminated diskettes
- Pirated software
- Infected proprietary software
- Fake games - some virus programs pose as games software. Many users like playing games and virus spreads fast by use of games.
- Updates of software distributed via networks - provide widespread and anonymous propagation
Virus symptoms (manifestations)
- Unfamiliar graphics or quizzical messages appearing on the VDU
- Programs taking longer than usual to load
- Disks accesses seeming excessive for simple tasks
- Unusual error messages occurring more frequently
- Less memory available than usual
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- Programs or files mysteriously disappearing
- Executable files changing size for no obvious reason
- Changes to disk volumes identifications
Virus protection
- Make backup copies of your data on a frequent basis
- Protect data on your floppy disks by using write protect tabs
- Turn off your computer when you are not using it
- Avoid downloading computer games from electronic bulletin boards
- Limit your use of “shareware”
- Do not loan out your utility or other software programs
- Run virus protection programs frequently
- Never open an email attachment if you have even the slightest doubt about its origin