INTRODUCTION TO COMPUTER

  

INTRODUCTION TO COMPUTER

Computer comes in different variety of shapes or forms and is used extensively in business, science and several other areas. Computer is now widespread because of its ability to perform all kinds of task with speed accuracy.

It is important to note that general purpose computer (what is a general purpose computer) are not pined to a particular task, if it appear so to you, may be because you are using the computer for that task, this task can be found controlling traffics in the cities, automated lines, factory production lines, automated warehouses, air-crafts, ship, x-ray machines in the hospital, missile controlled equipments, nuclear weapons, automated defence and so no and so forth. However, special purpose computers are limited to a routine service or task they perform. They can be found in cameras, filling station, locks, cars, watches, TV games and so on and so forth in their basic and miniaturizing forms.

 

WHAT IS COMPUTER

Computer is an electronic device or machine that receives, stores, processes, and transfer information accurately at  a very high speed without human intervention (means automatically)

              In other words, computer is an electronic machine or device that is capable of accepting user’s data through input and processes the data according to instruction given, thereby producing useful information as output (information)

 

DIVISION OF COMPUTER SYSTEM:

Computer system is divided into three major’s area as shown below:

1. Hardware
2. Software
3. People

Most computer text books may not talk about the three last divisions of computers. It may not be put in place that without a great deal of mental effort we can all agree that computer system must be operate by a computer personnel or a user in order to make it work. It therefore means that people who operate the computer constitute part of the system to make it’s a complete circle.

Each of this division has been broken down as follows

1. Hardware

Computer hardware is simply the physical components of the computer, they are those part of computer that you can touch and carry e.g keyboard, system unit (SU), visual display unit (VDU) mouse, printer, modem (modulator and demodulator), digital cameras, scanners, digital plotters, cables, un-interrupted power supply (UPS)etc.

2. Software

Computer software are refers to as set of instructions (programs) implemented either on hardware or firmware to make the computer usable. They are usually put on installed inside the computer through a set of diskettes or CD plate to make the computer perform effectively.

 3. People 

who operate the computer constitute part of the system to make it’s a complete circle.

Usually, the head of a computer department or the programmer, it could also be a system analyst that carries out this high level  of installations.

This high level of assignment will be segmented into programmer, it could also be a system analyst that carries out this high level of installations.

This high level of assignment will be segmented into programmers, system analyst, and operation managers. Each heading his section of programs; system design and final operation.

• Programming segment involves writing computer programs using selected high level languages e.g basic, COBOL, FORTRAN, pascal etc there could be many programmers at different levels including assistant programmers depending on the organization.

• System analyst segment covers, completes structure and design of the entire system. They work in-hand with programmers to come up with a good system. In fact, the work of a system analyst and that of programmer takes the form of architecture at a bolder level the two must go together or there will be a serious untidiness.

• This covers all form of computer operation depending upon what is obtained in the setup. There could be data supervisors, operators, computer technicians, data entry clerks. This segment ensures the full operation of information integrity of data entries transaction and reports production e.t.c

Other staffs that an be found under all the 3 categories above are shown as fellow;

1. Computer laboratory
2. Computer lab attendance/center cleaners
3. Messengers

The duties of attendees, cleaners and messengers are self explanatory

CHARACTERISTICS OF A COMPUTER SYSTEM

The characteristics of a computer system are numerous but only the vital ones have mentioned here to build an idea and perhaps pave way for further explosion in that regards, they are:

• Ability to accept/store user data and instruction (programs)

• Ability to obey sequencing of instructions.

• Ability to perform simple and complex calculations

• Ability to operate or perform task automatically that is without human intervention.

• Ability to communicate with other system device and machines

• Ability to use simple logical rules to make decision for its own internal control or external activities

• Ability to store very large volume of data for immediate or later processing and subs equal production

• Ability to control simple and sophisticated such as robot, flights, ships nuclear weapons, production lines etc

• Ability to exploit a complex internal structure of electronic circuitry on a variety of ways.

BENEFIT / IMPORTANCE OF COMPUTER

1. Very fast: most modern computer s can performs operations such as addition subtraction, other complex computation (speed) measured in billion of a second (nanoseconds) and even trillion of second (pico record) this means that the average computer can read thousands of items, process them and produce them and produce information in a relatively short time.

2. Accuracy: when a computer is correctly programmed and input is properly carried out, the accuracy of  the output is virtually guaranteed.

3. Large storage capacity: computers have the capability to stored millions of items ranging from data and programs.

4. Cost effectives: this could also be related to cost saving when we look at from an angle of respective performance, especially in businesses setup, such as oil exploitation project general research, weather forecasting etc this will not be feasible without the uses of computers. Etc.

COMPUTER CONFIGURATION AND ARCHITECTURE

Computer configuration:

Computer configuration refers to the setup or simply physical arrangement of a computer system. The way the computer is being arranged, how program are setup in-side the computer is referred to as computer configuration. This  is talking about software installation and hardware generally.

COMPUTER ARCHITECTURE

Computer architecture on the other hand refers to the internal arrangement of a computer system e.g arrangement of register, memory, processor, and its drives respectively, these are powered on can tell you about its rams, hard disks size and every other hardware attached to the system.

UNIT OF COMPUTER SYSTEM

the hardware components of a computer system, consist of a system inter-connected electronics and mechanical devices, any computer machine, be it a pocket calculator a super or mainframe computer, they all have the same parts.

Auxiliary storage:

This storage actually supplements the main memory. This is not the parts of the central processing unit, but the component is housed by the CPU for easy accessibly. This is made up of different form. It could be the hard disk or diskettes

Central processing unit:

This is the main component and it is also referred to as the brain of computer. The cpu has three parts as follows

Control unit:

This is part of the CPU where the entire operation is taking place. All parts of computer receives signal from the control unit. This could be the control of getting information printed on a paper

Etc

Arithmetic’s and logic unit (ALU) 

This helps in carrying out simple and complex calculation. A logical operation needed to process data. Good example of the logical operation could be true and false etc

Processor:

Arithmetic logic unit (ALU), control unit (CU) of the CPU are separate from memory, because the memory size work independently from the control  unit and ALU therefore the control unit and ALU unit are known as the PROCESSOR, the speed of the processors, the memory size and the storage has the ability to determined the performance and so the cost of a computer system, they affect micro computing and that’s why is been improve upon.

Input Devices:

This refers to as any devices with the capacity of taking in Data into the computer system . example of this could be a card reader, visual/video graphic adapter cable (VGA), mouse, keyboard, microphone, that takes in sound into the computer system, etc.

SYSTEM SOFTWARE AND APPLICATION SOFTWARE. 

System software

These are software’s that computer system required to be able to run and control the entire operation of the computer. A very good example include ms-windows, unix, NT, Disk operation system (DOS) or Microsoft Disk operation system (Ms-Dos) the other system software or program with extension names such as SYS, COM, EXE. Provide assistant in making the program or computer operation

Application software

These are programs or packages designed to meet computer users need (user’s software). A very good example of these includes: Ms word, Excel, Corel draw, AutoCAD etc.

TYPES OF COMPUTER SOFTWARE:

System software’s are the DOS, MS-DOS, and program with extension names such as system, com etc. these programs handles jobs arrows scheduling, memory management band and so on.

Application  software:  Are categorized into application programs and application packages. Application package are further categories into general and specific

The general packages are the database management system (D-BASE) spreadsheet, like Lotus 123 Microsoft Excels etc.

AREA OF APPLICATION OF COMPUTER

The computer unlike in the past is finding more and more application in so many areas of human endeavors. The reason is the advancement of technology; especially information technology which has rigged off an evolution wide area of electronics. Computer is often used for planning, decision making and control purposes, this include areas of education, health, industries and the government. In fact every area is now benefiting from the use of computer systems.

1.  EDUCATION

There are two major objectives of utilizing computer education. One is to teach people about computer, (computer literacy program) and the other is to teach the traditional subject areas; the way computer function and their impact on their everyday lives. “We must become computer literate”. The literacy can be acquired through academic programs, computer application courses.

2.  Health

The use of computers in health field has actually resulted in better medical diagnosis and has enhanced peoples’ lives. The following  are general application areas of computer in the health’s field;

i.    COMPUTER ASSIST IN DIAGNOSIS AND RESEARCH

One advantages of computer is that, they free doctors from the routine testing procedures. These result conserve time and enable them to give more attention to patient’s treatments. Some medical doctors are now using the computer diagnosis tools in hospital and clinic at a numbered of multiple screening centers; patients are given physical examination, consisting of series of various electrocardiogram chest x-rays, urine test, Blood pressure measurement, Lung infection, vision , hearing . Etc

ii.  MEDICAL HISTORY PREPARATION AND RETRIEVAL

To develop patient medical history, doctors and nurses asks patient series of questions about their past illness or health of blood relatives, A number of software application packages are available in these areas.

3.  INDUSTRY

Computer have been effectively use in many instance to control he overall production Process in many industries. Also without computer the ability of traffic controllers and other assembly plants and robots which are computer controlled machined are typically used for performing tasks with high precision.
4.  BUSINESS
The basic goals of business are to maximize profit and minimize loss and cost. Computers are the most effective when it comes to achieving these objectives.
The following are functions of computer in business environment;
a. To reduce the need for human records keeping.
b. To reduce the numbers of errors proceed in record keeping  operations.

c.   To store data efficiently

PRE-COMPUTER AGE (BRIEF HISTORY OF COMPUTER SYSTEM)

The history of an attempt to make machines that can perform long sequence of calculation achromatically, moreover, before the invention of electronic computers, there had been different mechanical machines that carry out these operations.

Example:

BABBAGE ANALYZING ENGINE

In 1822, Charles babbage an English scientist began work on a device called the different Engine, which was designed to automate standard procedure for calculating the root of polynomial) it was later abandoned for a more powerful device known as analytical Engine which was remarkable similar to twentieth century digital computer.

Analytical engines was designs into two types of card one called operation card to indicate or specify the actual data. Babbage conceived of two main units for his analytical engines.

i.   An area called a story within the device in which instructions available would be placed.

ii.  Also another area called a mill in which arithmetic operations would be performed. Babbage was considered to be the Father of the modern computer on his work. 

HETMAN HELLERTH

In the 1890’s Hetman Hollerith who was working for united state census government department, devised electrical tabulating equipment that was used gathering census data. The essence of this contribution was a method representing information by a series of punched holes on paper card. He also developed electrical equipment that would tabulate information from this card and to sort the card by some criteria such as sex, age, marital status etc.

Hollerith eventually left the census government department and formed his company to produce this equipment. With time his company merge with others and the result was the birth of IBM which today is still a market leader in U.S.A.

JOHN MAUCHLY AND PRESEPER ECKERT

In 1946, John mauchly and preseper Eckert completed the ENIAC (Electronic numerical Integrator and Calculator). It was the large scale electronic digital computer ever built. It contained 18,000 tubes and could carry out 300 multiplications per second. It was programmed by connecting various wires to the units and setting up to 6000 switches in such a way that the conceived program could be executed. Eah time a new program was developed the wiring had to be redone. The ENIAC mainly used for engineering calculations, ballistic table, weather prediction, atomic energy calculation etc.

ABACUS:  counting machine using pebbles to represent quantities.

PASCAL: produced in1673, improved on the aid of additions and subtractions.

LEIBNIZ: in 1673 improved on pascal and developed a technique for division and multiplication. There are several others contributions but advancement on these instructions gave birth to other machines such as:

ERVAC: Electronic discreet variable automatic computer developed in 1948.

UNIVAC: Universal automatic computer developed in 1951

The above inventions identified a principal “STORED PROGRAM CONCEPT” to which the success of storage in all computer generations can be credited to:

TYPES OF COMPUTERS

1.  CLASSFICATION OF COMPUTER BASED ON GENERATION

2.   CLASSSFICATION OF COMPUTER BASED ON TYPE

3.   CLASSIFICATION OF COMPUTER BASED ON SIZE

4.   CLASSIFICATION OF COMPUTER  BASED ON PURPOSE OF USE

CLASSIFICATION OF COMPUTER BASED ON GENERATION

As mentioned on the history of computer earlier, the history of computer is long, but it is classified according to generation of the computer and we have five generation of computers history or to say that computer have gone through five generations. Since 1940s the trend has be a gradual fall in the size of CPU over the last decades. For instant, 1980 micro processing unit (MPU) occupied 1/500^th of the area occupied by a compared 1960 CPU and size was getting small.

 

FIRST GENERATION (1945 TO 1955)

These were computers made “between” (1945 to 1955). They were made of valves vacuum tubes for internal circuiting, very large, bulky, un-reliable, consumed a lot of power and generate high rate of heat e.g Univac (universal automatic computer)

SECOND GENERATION (1955 TO 1964)

These were computers develop “between” (1955 to 1955). They were using transistor to replace valves vacuum tubes, low symbolic language, operating system, magnetic disk, Binary numbers and assembly language. Example was the IBM – 7094 develop.

THIRD GENERATION (Early 1964 to 1974)

These were computers made “between” (1964 to 1974) and they used integrated circuit in which transistors and other components where manufactured on silicon chip. They are 100,000 times faster than the 1^st generation computer, and they become the “main frame” computers.

FOURTH GENERATION (early 1981)

These were computers made “between” (1975 to 1985). They use large scale interrogation (HSI) with thousands of transistors, capacitors and silicon and interconnection wiring were built in fewer silicon chips, LS large storage, high speed, less scale of heat generation, reliable and very portable. This was the era of powerful micro computers.

FIFTH GENERATION (early 1981)

These were computer made between 1981 to date. They are multimedia system that can play music, films, communicative with the world through internet. Some 5^th Generation computers control missile, nuclear weapons, air-crafts, ships. Some controls production lines others take sophisticated photograph and buil behave like being, reason, and act without being prompted.

 

CLASSIFICATION OF COMPUTER BASED ON TYPE

they are classified in to digital, Analogue and hybrid computer.

• Digital Computer

Accepts inputs as discrete or Numbers coded in binary digits and performs mathematical calculation on them. They are the type used in commercial applications. They give very accurate result.

• Analogue computer;

Accepts data as continuous variable quantities such as voltage resistance, temperature, pressure etc. there uses are mainly restricted to scientific and engineering functions. Car speedometer and service station petrol consumptions are analog devices to the latter, the flow of gasoline fuel is converted into the price of the desired gasoline to the nearest kobo and quantity of pumps fuel to the nearest tenth of a line.

• Hybrid computer;

These are computer that are use combine the both feature of digital and analogue devices like those used in missiles and spacecraft programs. They operate continuous variable and discrete values.

CLASSIFICATION OF COMPUTER BASED ON SIZE

These are computer  classified based on size and performances. They are :  

Super computer: Used to huge “number  crunching” application mostly in scientific areas such as weather forecasting,  medical research and space program control of nuclear weapons and missiles, found in developed countries today.

Main frame computer: these generations of computers are usually very large and expensive

Main computer: they follow the main frame and smaller in size when compared with the main frame.

Micro - computer: are in difference shapes, sizes, and it can be used to perform varieties of activities. They are powerful, easy to carry, simple to operate, very common, cheap and generate less heat, example of those computer are: tower, mini tower, desktop, laptop, notebook and palmtop computers etc.

CLASSIFICATION OF COMPUTER BASED ON PURPOSE OF USE

They are classified into special purpose also known as dedicated duty computers and general purpose computers. The special purpose computer made t handle special tasks of job and nothing other than that while general purpose computers can be used handle various kinds of task, job or activities.

1. Special/Dedicated computers: as the name suggests, they are designed to perform a particular job only. Those designed for air-traff control, robots in car manufacturing or assembly plants and weapons guidance system.
2. General purpose computer: is design to solve varieties of problem. Thus, general –purpose computer could be applied in a number of areas like comers, engineering, education, space programs; e.g. weather forecasting etc.

HIERARCHICAL SYSTEM OF DATA

CHARACTER: A character is the smallest unit of information that can be stored in a file.

1. It made up of:
2. Numbers:- 0,1,2,…to infinity.
3. Alphabetic:- a, b, c,….z
4. Special characters:- >, <, +, =, etc.

BIT: are binary digits that represent characters in the main memory e.g. 25 in binary is 11010, I is an on-bit while 0 is an off-bit etc.

BYTES: a byte is a set of consecutive Bits. By IBM standard Bits = 1 bytes

WORD: this is made of bytes. Memory may be divided into a group of fixed number of bits per location e.g  8, 16, 32 bits. Such a group forms a word, the word (Length refers to the fixed number of bits thus 8 and 16 bits in microcomputer for example, are said to have 8 and 16 word length respectively).

FIELD:  A field is a unit of information in file. It also referred to as data item. It is made of characters e.g DEPT     M16

RECORD: A record is a collection of fields

FILE: A file is a collection of record about an activity

DATA: Data can be defined as raw fact. It is also referred to as unprocessed information.

INFORMATION: Information can be defined as processed Data.

LOCATION: This is the place where characters are stored binary digits.

STORAGE: Memory is expressed usually in terms of bytes, kilobytes (KB), Megabyte (MB) and Gigabytes (GB). 1 kilobytes = 10224 Bytes and Kilobytes are use for small computers like micro-computer while Megabyte is use for the bigger machines like the minicomputer and main frame computer. 1MB = 1 million approximately.

COMPUTER FILE

A file consists of a number of records. Each record is made up of a number of fields and each filed consists of number of characters.

TYPES OF FILE

A file consists of a number of records. Each record is made up of a number of fields and each filed consists of number of characters.

TYPES OF FILE

1. Master files
2. Transaction or movement file
3. Backup files
4. Scratch files

MASTER FILE: These are files that contain important record of information, such as the original customer record for a business. A master files may simply be a list of names and address but it must contain the last update. Information about the master file is always the one that is consulted. E.g. sales, report, employee record etc. It is the main file where business activities are consolidated.

TRANSACTION OR MOVEMENT FILE: These are files or data currently awaiting some action. The sort of data that the transaction file may contain is the information that a customer has just paid or another customer may have had some goods dispatched to them. The transaction file is usually used in conjunction with the master file to produce a new master file containing the most update transaction that occurred. The situation is shown in the figure bellow,

These transaction file may be used to update the master file daily, weekly, monthly or even longer depending on the needs of the company or the urgency with which the data is needed.  The transaction file is usually produced offline perhaps, using a key-to disk or a key tape on the transaction file ready for updating the master file automatically. It is likely that some sorting of the transaction file would be necessary so that the transaction presented to the computer later on when the educating takes place.

BACKUP FILE:  this is a general name used for files which are simply copied of the original files. They are needed in the event of a hardware or software errors or more likely, human error that causes loss of data in either the master or transaction files.

SCRATCH FILES: often a computer run will generate a file that contains data that is no longer needed. An example of a scratch file may be the magnetic tape containing some that have been sorted and transferred to another magnetic tape for processing.

FILE OPERATIONS

CREATING A FILE: before any file can be used it must obviously be create, often this involves creating a file that consist of dummy data such as being resend into all the files. This task is usually carried out under the control of a special file reaction programmed.

FILE MAINTENANCE: usually involve insertion and deletion. Insertion means bringing new record into the master file and deletion means removing record from the master file.

UPDATING:  this is the progress of bringing the content of a master file to reflect current circumstances/situation.

FILE INTERROGATION  / INQUIRY: is usually carried out at the instance of resolving a problem or response to an inquiry e.g. responding to a request from a customer wishing to know the balance of his bank account.

RETRIEVAL OF DATA: this is the operation which is most often performed on a file it is the process of funding displaying or printing a particular record in a file. Effective file maintenance is essential if the files are to be kept in an accurate and complete way. File maintenance also involves such process as making backup copied of file in case of hardware or software malfunction.

TYPE OF PROCESSING

OFF-LINE PROCESSING

OFFLINE:- This is a situation in which a device is linked or connected directly to the CPU (central processing unit) and under its control. E.g. diskette in its drive, the CPU is used transferring data. Off-line processing data transferred can be processed immediately or allowed to accumulate for processing in the near future.

ON-LINE PROCESSING

ONLINE:- this  is the process in which all the component of the computer system such as CPU, VDC, keyboard are directly communicate with each other.

Note: on line processing is an expensive  method because of the extra cost of providing terminal; locations in close proximity or remotely.

Areas of application of on-line processing

Reservation of a hotel room for tourists.

Reservation of car in car-hire service.

TIME SHARING PROCESSING

Responds but if something is wrong an error message is displayed which will now prompt the user to table corrective action. The job structure of a typical data processor department as shown above

PERIPHERAL DEVICE

They are the components of computer system that are attached to the CPU or outside the CPU, they comprises of input device (Mouse, Keyboard, and Scanner etc), output (Monitor or VDU, Printer etc.) and Auxiliary storing device (Diskettes).

VALUE DISPLAY UNIT (VDU)

Types of Visual Display Unit (VDU), CRT, LCD

this is also called video console or monitor. It is a television like device which computer use to display information or picture. There are monochromes and color display text or graphics in different color called background. There are different types of color monitor they are:

CGA Monitor (Color Graphic Adapter), 16 color and lower resolution

EGA Monitor (enhanced Graphic Adapter), about 16 color good resolution

VGA Monitor (Video Graphic Adapter), bout 262, 144 color and very better resolution.

SVGA Monitor (Super Video Graphic Adapter), with 262, 144 colors an excellent resolution.

KEYBOARD PARTS

This is an input device which looks like a typewriter that we know and it use enter information into the computer. The keyboard is divided into many parts as illustrated below:

Alphanumeric keys: they are A-Z , 0.9, keys

Function keys: they are the F1, F2 and so on, used for special purpose

Scroll keys: they are the page up, page down, home end and 4 arrow keys.

Number keys: they are the keys arrange by the right hand side of the computer keyboard.

Special keys: they are ESC, Shift, Tab, Ctrl Alt etc.

MOUSE & MOUSE MAT/PAD

A mouse is an electro-mechanical device which is used to perform some of the keyboard functions like cursor movement, menu selection etc. it comprises one, two or three buttons and each has a work to do. Mat/Pad is puts under the mouse to ease movement and minimize data.

DISK DRIVE

There are three types of drive;  a hard disk drive (labeled c), a floppy (labeled A) removable disk (labeled E). A hard disk is a non removable disk that is built into your computer. This stores large amount of information conveniently. Sometimes having such large information on the computer system can cause the computer to delay, other causing trouble and wasting of one’s precious time. Is a removable disk which can be inserted or slotted into the drive of a computer system to retrieve or store information on it. This has less storage capacity compared with the hard disk and accessibility of information is lower than that of the disk drives which is very fast.

Each of these disk drives has a letter assigned to it which tells out where to find or store information in the computer . hard disk drive is called drive  while floppy disk is called drive a. however, because a and  are used, drive d or drive e is for CD drive (compact disk).

STORAGE MEDIA OR DEVICES

MAGNETIC DISK / TAPE: this is similar to those used in tape recorders. It is serially  accessible or a magnetic disk which looks a gramophone records with information record on them magnetically is accessed in disk randomly as against serial accessibility in tapes.

FLOPPY DISK are common but a typically example of fellows:

Most programs today are recorded on CD (compact disk) and most computer come with CD compartment to be read from the CD while the use of 3.5 or 31/2 drive is still in used but the used of 5.24 or 51/4 drive is out of used. The computer CD is just like any other CD play and any CD plate, can be view or play in the computer so log as the computer has a sound card / video card installed in it, in a nutshell  the system should be multi-media. Another CD recorded is the , re-writable used for writing or copying data lie program, Audio and video to CD plates. The audio / video mean sound and images separately can be copied to CD plates.

COMMUNICATION PORTS

These are slots on which all the computer computer components devices or hardware are plunged or connected to the CPU. The ports also used to establish communication link between the computer and the devices like the scanners. There are other cables such as the power cables for connecting the CPU or VDU to the source, mouse cable to the CPU, keyboard cable communication cable to CPU (VGA able) and so on. All these are done using the ports.

CABLES

These are insulated wires used for connecting the computer (CPU) to other devices or components for conduction or transmitting current of signal from one point to another. These cables are:

• System power cable

• VDU power cables or CPU to VDU power cable

• Printer power cable (parallel, serial or USB communication cable)

• Disk drives controller cables

• UPS power cable or UPS to system cable etc

MEMORY CHIP

This is an on-line store where data and information are kept during programs executing and  processing. This is segmented into ROM and RAM.

ROM.

Read only memory (ROM): is an area or part of the computer memory that contain information which user can not alter but only read from. It is station and usually small in size.

RAM

Random access memory (RAM) is an area or part of the computer memory and usually from the major proportion of main memory that contains information which user has a direct or indirect access. It is large in size but volatile and so lost when the power goes off. To keep permanent information you need to save it in the backing strode or auxiliary storage (secondary storage) which in this case may be a floppy or hard disks.

MOTHER BOARD

it is called the base board or main system board. It is the main circuit board on which all adapters, cards chips, disks controller, mouse controller, keyboard controller, processor chips, printer controller, and other interface card are attached. It uses number of bits to send data depending on the capacity of the type of memory size and processor.

PRINTERS

These are used in producing information out from the computer to either the VDU to display the output or directly to the paper via the printer. There are many types but the major ones are the impact and non-impact printer.

IMPACT PRINTER

The printer hard makes physical contact with the paper. They are noisily and slow e.g dot hart printer like LQ Epson printers.

SOME IMPACT PRINTER COULD BE:

Characters printer:- it prints characters at a time

Lone by line printer:- it prints line of as text at a time.

NON IMPACT PRINTERS

There are printers scan the content of a memory page by page and produce same on paper with sharpness (high resolution) e.g laser printer.

SCANNERS

Scanners: allow you to get printed material view into your computer, which can then be stored in the computer. These pictures can then be altered, resized and printed as required.

OTHER COMPUTER

There are devices such as:

• Modern (modulator and demodulator) used with telephones lines

• Digital camera used for taking all sort of pictures usually produced by the computer

• Scanners for scanning images and texts.

• Surge protector which protect the unit connect to it against surge

• UPS un-interrupted power supply (backups) which retain power electricity fails

• Stabilizers for stabilizing current and so on.

DISKS OPERATOR SYSTEM (DOS) OR (MS-DOS)

Ms- dos like other operating system manages the flow of information in the computer. Dos or ms-dos manage the entire activities of a computer system from the time the system is put on to the time it is put off. In fact, without the disk operating system computer cannot be operated at all. Dos or ms-dos includes commands that can be used to perform task such as:

• Memory management

• Manage files and directors

• Maintain disk

• Job scheduling

• Error handing

• Configure hardware

• Speed up programs

• Customize ms-dos

• Optimize memory usage etc.

COMPUTER PACKAGES:

These are application package or software of programmed specifically design or prepared to handle some certain tasks or jobs so that the load programming is reduced. The only thing is to known to operate such packages to be able to accomplish your jobs using the computer as explain above. Good example of some of such computer packages are listed below;

• Microsoft world/word perfect. Write. Word and note pad etc

• Lotus 123 Microsoft excel

• Database management system (DBASE)

• SPSS (statistical package)

• Card/shop/instant artist/Corel draw

• Venture publisher / page maker / Microsoft publisher

• Peachtree accounting

• Pegasus etc

WHAT COMPUTER CAN DO

To state all what computer can do is to prepare to write an endless book. I used the word endless because the professional is very dynamic. It is full of wonders and of changes what you known today. There will be a new one and upgrade of its tomorrow. Infect no human being alive who claim that he has never seen or heard some of the activities and a lot of computer tasks regarding in both government and private organization. Today several individuals have their own computer in their home. The firms we watch keep telling us a lot more about computer. The aim and effort to make the whole world a global village which is very recent development has been achieved b y the introduction of internet and its related services.

COMPUTER VIRUS

Like the biological virus computer viruses are sets of programs deliberately and legitimately written by computer programmers to protect there work from piracy (copyright). The virus spread when exposed to its favorable state by adding itself to an existing of executable ode so that it is executed along with the host code when it is run.

CLASSIFICATION OF VIRUSES

Major classification of virus is based on the sort of executable code with which they attach themselves.

PARTITION VIRUS

The partition virus is found at the sector of the hard disk. It is also referred to as master boot record it contain some information for starting up the computer. A partition virus will find it place on this sector thus making it difficult for the PC to ensure the code found there.

BOOT VIRUSES

These viruses affect the boot sector of the floppy or hard disk when from drive A or C when you switch on PC, it first read the sectors of either drive  or A, boot sector will replace this sector with its own code moves the original code somewhere else on the disk, these making booting impossible.

OVER WRITING VIRUSES

These are viruses that overwrite all or part of a program and making it difficult for the programs to run. Other viruses are: resident virus, Trojan, etc.