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A computer is an electrically powered device or set of devices which works under the control of a stored programme. It automatically receives data, process data and by controlling the whole process of operation, the desired goal is established. Hence a computer is 1. a data processor, a storage location and a data processor. The following concepts may be used for the identification of a computer:
•Literally, the term computer means equipment that can compute.
•The computer is a combination of electronic devices used to process data.
•In the computer all types of data is converted to numbers. The computer can only work with numbers, not letters, sounds or pictures. All forms of data are converted to numbers for processing.
•Computers can receive, analyze, store information and produce reports.
•Computers are useful for accurate and fast processing of accounts.
History of Computers
•On about 3000 BC ‘Abacus’ was invented in China which was the earliest calculator. It was used for addition, subtraction, multiplication and division.
•On the 17th century a number of instruments were invented which could be used as calculator.
•On the 18th century a French scientist named Jacquard, invented an automated loom that could receive designs from punched cards.
•At a certain step of perpetual research, came Charles Babbgae with unique ideas. He is often called the father of modern computers. He invented ‘Differential Engine’ on 1812.
• He performed fast calculations with this machine. On 1833 he planned to make a ‘Analytical Engine’. This research did not go far due to hindrance of promised fund by the Royal Society of England.
• Later Lady Ada Augusta invented a number of techniques, which utilized the concept of the Analytical Engine. She was the daughter of the English poet Lord Byron and a close friend of Babbage. She invented the techniques required to solve mathematical problems, step by step. This is why she is considered as the first computer programmer in the world.
• On 1944, A machine called ‘Mark-1′ was built under the supervision Professor Howard Eken of Harvard University of USA. This machine was 51 feet wide, 8 feet high. It had 5000 miles of electric cable and combination 7.5 lakh electronic parts. Though a dinosaur among today’s neat compact computers, this was the first computer of the first computer-age (1944-50).
• The ENIAC (Electronic Numerical Integrator and Calculator) was built in the University of Pennsylvania on 1946; it consisted of almost eighteen thousand valves. It was made for the Ministry of Defense. In 1948 transistors were introduced, which ultimately replaced the valves. Transistors are miniature electronic switches that functions the same as the electronic valves and then some. 1958 saw the introduction of Integrated Circuits, popularly known as IC, which made the huge availability of computers today possible.
• Then came Gordon Moore on 1971 with his revolutionary invention of microprocessors.
• After the microprocessors, the progress was fast. IBM of USA introduced Microcomputers, which is now popularly known as PC or Personal Computer.
• The speed of data processing depends on how powerful the processor is. Currently processors with speed above 500 MHz is available in the market.
• The latest magic in the computer world today is the Internet; virtually the whole world can be reached through this little box with an Internet connection.
• We conclude, on the note that the computer has become an inseparable part of the modern civilization.

Hardware

• The term hardware refers to the part of the computer that you can touch namely the various types of equipment and peripherals are the hardware of a computer. For example: CPU, monitor, keyboard, mouse etc.
• Each type of hardware of the computer has a specific or several functions. For example: keyboard and mouse are used to input data into the computer. The monitor is used to display the output. The block diagram below lists the most common hardware of the computer.

Inn view of the above light, it is evident the following hard ware devices may be conceptually exemplified.

Device: All hardware peripherals of a computer are called devices.
Input device: A device through which data is fed into the computer. For example: keyboard, mouse, and scanner.
Process Unit: After the data is entered into the computer it is processed to produce outputs. Processing is done by the microprocessor.
Output Device: The devices through which we can receive the processed information are the output devices. For example: printer and monitor.
Memory
Memory is the computer’s electronic scratch pad. Programs are loaded into and run from memory. Data used by program is also loaded into memory for fast access.
RAM (Random Access Memory): The most common type of memory is RAM. It is volatile memory, as it needs constant supply of power. When you turn off a computer, everything in RAM disappears.
ROM (Read Only Memory): This is nonvolatile memory. Data and instructions are permanently programmed in this type of memory.
Storage Unit
It is possible from a computer to function with just processing, memory, input and output devices. To be really useful, however, it also needs a place to keep program files and related data when it is not using them. The purpose of storage is to hold data.
The device that holds a disk is called a disk drive. Some disks are built into the drive and are not meant to be removed. For example: Hard disk. Other kinds of drives let you to remove and replace disks, such as a floppy disk drive.
Introduction to some common computer hardware
Processing Unit The brain of the computer. This is where data and instructions in are processed to produce meaning ful information.
Hard Disk Fixed, built-in storage unit of the computer.

Floppy Disk Removable storage unit of the computer. This device has much less storage capacity than hard disks.
CD ROM Also a removable storage unit. This device has larger storage capacity than the floppy disks. It is a rounded thin plastic disk. A CD-ROM drive is required to read from CD-ROMs.

Monitor This output device is like a television screen that displays output such as a text that you are typing.
Keyboard An input device. It is an electronic version of the typewriter machine. There are special function keys, alphabets, numbers assembled on the keyboard. There can be 101 to 105 numbers of keys on a keyboard.

Mouse An input device. You can click, double click and drag with a mouse. Click is when you press a button on the mouse. Double click is clicking twice in rapid succession. Drag is to press a mouse button and ‘drag’ the mouse physically as the button remains pressed.

Printer Output device that produces hardcopy outputs. It prints out the output such as processed data, reports on paper. There are different types of printers available at different price ranges. Most commonly used nowadays are dot-matrix printer and Laser printer.
Floppy Disk Drive Used to read from and write to floppy disks. It is like an audio cassette player. You must insert the floppy disk into the floppy disk drive. It can read from and write to the floppy disk.

CD ROM Drive Used to read from CD ROMs. It cannot write to a CD ROM.
CD ROM Writer Used to read from and write to CD ROMs.
Scanner Input device used to scan image or text and put a digitized version into the computer’s storage unit.
Speaker Output device for sound or acoustic data. Same as a speaker in the audio cassettee player.
Modem This is a communication device used to access the Internet or other computers through phone line.
Introduction to power appliances normally used with computers
Stabilizer We are all familiar with the voltage up-downs in our electric supply. Both High and low voltage can be harmful to the complex electronic circuits and devices inside the computer. A stabilizer is used to produce a static supply of power in the face of disturbance in the actual supply. So using a stabilizer with your expensive computer is very much recommended.
UPS uninterrupted Power Supply. This appliance is useful in face of regular power failures. It generates power when the main power supply fails and gives a user some time to shut down the computer properly.
Hardware and Software
Let us discuss these two commonly used terms in the computer literature by comparing them with a common example, the audio cassette player. What do we do when we want to listen to our favorite songs? We first insert an audiocassette into the player and switch the player on. Then press the ‘Play’ button, and consequently the music starts. But notice that we listen to the song, but we cannot ‘touch’ the song. In the computer literature the player and audiocassette are HARDWARE and the song itself is the SOFTWARE. The difference between the song and software is that while, song has no control over running of the cassette player, software is the main controlling force of the computer’s hardware. Without the software the computer hardware is just a dead machine.
Another relative point to mention here is that computer cannot automatically perform a task. It can only do jobs that have been programmed into its memory and programmers do all the programming. Programmers are the people who write codes or instructions for the computer to understand and work accordingly. The information and instructions that have been fed into the computer’s memory to perform a specific task is collectively known as software. The computer can be programmed to do almost anything with the right set of instructions and codes; i.e. there can be numerous types of software, one or more for each type of task imaginable. For example software can be specially written to draft letters, memos or documents. Another type of software can be developed to do your daily accounts, i.e. addition, subtraction, multiply and division. Special types of software are written just to keep the computer running. They create environments to enable other software to run.
We can define software as follows:
•Software is sets of data and instructions to control the computer hardware, to perform various tasks such as producing complex mathematical and logical results.
Categories of Software
Most software falls into two major categories: system software and application software. One major type of system software, called operating system software, tells the computer how to use its own components.
Application software tells a computer how to accomplish specific tasks for the user such as word processing (MS Word), drawing (MS Paint), spreadsheet (MS Excel), presentation (MS PowerPoint) etc.
BIOS
When you turn on a computer, it goes through several steps to prepare itself for use. The first step is a self-test. The computer identifies the devices that are attached to it, counts the amount of memory available and does a quick checkto see whether the memory is functioning prperly. This routine is called the BIOS (Basic Input Output System) and is located in read-only memory (ROM).
Operating System
Next the computer looks in the floppy disk drive and then the hard disk drive for a special program called Operating System. The operating system tells the computer how to interact with the user and how to use devices such as the disk drives, keyboard and monitor. Windows98 is an operating system software.
Application Software
A computer that is running only on operating system is not very useful because the operating system exists mostly for the benefit of the computer. Other programs are required to make the computer useful for people. Application software help users accomplish specific tasks. Appllication software has been written to do almost every task imaginable., from word processing to selecting a college to attend.
Windows
By now you must have some idea about what software is and its types. All software are developed on the basis of a predetermined objective. For example: Microsoft is a software company that has developed a number of window-based user-friendly software with the objective that a novice user should be able to use the computer to his/her advantage. Windows98 is one of its operating system software that is very user friendly. In all steps of the way, it helps the user with messages and hand signals.
Running a program in Windows
After you switch on your computer it shows various start-up messages and stops after it reaches a certain screen, for user intervention. This screen is your ‘Desktop’. You must click on the Satrt button to see the contents and programs stored in your computer. Clicking on any of these programs will make that program ‘run’. As an example let us run the Microsoft Word:
•Click Start button
•Click Programs
•Click Microsoft Word
Control Panel
Clicking on the Start button shows an option ‘Settings’. There is an option there named ‘Control Panel’. This folder contains programs that control the software and hardware of the computer.
Please be careful in using in any of these programs. Control Panel programs should only be worked on by a liitle more experienced people than the beginner.
List of some tasks the control panel programs can perform:
•Control Date and Time of computeAdd or remove new programs
•Install new hardware
•Install new printer
•Background look of the Desktop can be changed
•Change the configuration and speed of the mouse
•Others
Windows Explorer
Windows Explorer in its simplest definition, is the table of contents of a computer.
We can see at a glance, all the drives, folders and files that are contained in the computer, through using the Windows Explorer. A user can organize his/her files and decide which files should go into which folder, create new folders, cut or coy and paste files and folders etc. Also, a file can be copied to or from the floppy disk from or to the hard disk.
How to open Windows Explorer:
Method:
Windows Explorer Environment:
Folder
Folders are like file cabinets. You can organize your files in different folders as you choose. You can create folders within a drive; sub-folders can be created within a folder.
Creating Folders Open Windows Explorer. Click on File menu. Click New. Click Folder. This is illustrated in the figure below. The newly created folder is given the name ‘New Folder’ by default. You can rename it with a more relevant name and press Enter.
Delete a Folder or File
As mentioned before, to delete a file or folder is the easiest thing to do in a computer, so be extra careful of what you are deleting.
•Open Windows Explorer
•Click the file or folder you wish to delete
•Press the Delete key of the keyboard
Restoring a deleted file or folder
Deleted files and folders are actually moved to another part of computer har disk, they are not completely erased from hard disk. Deleted files and folders are kept in this separate portion of hard disk, which is called a Recycle Bin. You can restore a deleted file by clicking Restore in the Recycle Bin File menu. If you, however, Empty the Recycle Bin, deleted files and folders will be lost forever.
Restoring Deleted File or Folder from Recycle Bin
•Double Click on the Recycle Bin Icon of your Desktop.
•Recycle Bin window appears
•Click the file or folder you deleted and want to restore
•Click File Menu
•Click Restore
The figure below might make the steps clearer:
Cut, copy and paste
Preface: In our country, especially in Dhaka city, we are all too familiar with postering on the walls. For this, the posters are prepared in the press, then pasted using glue, to the walls. After pasting a poster to a particular place we might change our mind and take it off to paste it somewhere else, or we can make more copies and paste them to other walls. The postering aspect has amazing similarity to the cut, copy and paste options of a computer application.
For example: if you are preparing a document in the computer using a word processing software, you may come across a need to use the same word or phrase in a number of places. In which case, you can copy this word or phrase and paste it to various places of the document, instead of typing it so many times. You can paste a text as many times as you want after making a ‘copy’. Copy and paste also applies in case of files and folders in Windows Explorer. You can copy a file or folder and make as many copies of the same file in other folders or sub-folders, as you want.
If you want to remove a file or folder from a particular drive or folder and put it in a different folder or drive, just ‘cut’ it and ‘paste’ it to the place you want to put it. Similarly in our example of the document, you can ‘cut’ a word or phrase and paste it to other place(s) which will remove the word or phrase from the first place and move it to the second.
When you cut or copy a file, folder, text or image, it is temporarily saved in a place in the memory called the clipboard. When you click the paste option, the file, folder or text from the clipboard is pasted. This is why you can make exact copies of the same text, files, folders as many times as you wish.
Definitions, Terminology and Method of Cut, Copy and Paste
‘Select’ is the key word in the process of cut, copy and paste. To select is to mark a text, file, folder that must be copied or cut. You can click and drag the moue to select a text or click a file or folder to select. The selected text, file or folder will take on a different color (commonly black) to indicate a selection.
‘Cut’ as mentioned before, is the process of moving the selected text, file or folder from one place to another. In the Windows Explorer select a file; click on Edit menu or the toolbar and then click the Cut or copy option. In a word processor, follow the same steps.
‘Copy’ is the process of making replicas of a file, folder or text. The selected file, folder or texts remain in its own places and an exact replica is created on the clipboard. Clicking on ‘Paste’ toolbar or Edit-menu option moves this replica from the clipboard to the clicked place.
‘Clipboard’ is the place where the cut or copied information is temporarily stored.
To copy a file to Floppy Disk
•Open Windows Explorer
•Insert a floppy disk into the Floppy Drive
•Select the file you want to copy
•Click the Copy Button on the toolbar
•Click the A: drive
•Click Paste tool bar button
File Management
To find important files quickly, you should organize your files in easily detectable folders. For example: supposing there is number of files for the employees of an office, which contains the employee’s personal information, salary, previous experience etc. You can keep these files in a folder named ‘Employee’. Create sub-folders such as Personal, Salary, Experience etc and keep relevant files in those sub-folders. You should take a little time and thought to organize your files and folders, same as keeping organized records and files in an office.

Find a file or Folder
Sometimes it is easy to lose a file among a hundred other similar files. You can use the Find option in the Windows Explorer in such situation. But the catch here is that you must remember something about the file, such as its first 4 letters or last 4 letters or the date it was created or the folder it was created in or its size or some of the text contained in the file.
•Open Windows Explorer
•Click Tools menu
•Click Find
•Click on File or Folder option
•A Find dialogue box appears
•Type the info you remember about the file or folder
•Click Find Now Button
How to give electrical connection to Computers
To protect your computer from power surges, frequent power failures and other electric disturbances you should use stabilizers. Instead of directly connecting your precious appliances to the main power line, connect the computer to the stabilizer and the stabilizer to the wall socket. UPS are used as a temporary power source for the computer in case of power failure. The figure below shows the flow of electric connection among a computer, UPS and stabilizer.
How do Computers work?
To illustrate how a computer processes data we can use an analogy between computers and the human brain. The five human sense receivers are the input devices of the human brain. The eyes, ears, skin, tongue and nose receives different types of sensations and sends them to the brain for processing. Similarly the keyboard, mouse, scanner and other input peripherals of the computer collects different types of data and sends them to the processor to be processed.
The human output devices such as talking through mouth or physical gestures can be compared to the monitor or printer of the computer, which shows or prints the processed result from the processor.
Users and Phobia
Now that you have an idea on how to electrically connect the computer the next step is to work with it. Unfortunately, like all other new technologies, the computer has its own set of phobias for its users. Realistically, as we have pointed out before, to run a computer can be as easy as switching on the television. You can only do physical harm to a computer by breaking it or one of its components. The software that you will be using, can be itself a trainer/instructor for a beginner like you. This is because most computer software are developed in a user-friendly manner and has in-built help-option to assist or guide you through your ordeal. So don’t be abashed or apprehensive, switch on the ‘magic-box’ and get started.
Switch on the computer
See if the electric connections are as it should be and press the power button of the CPU. The computer screen will show various start up info and messages and will stop after a reaching a state and wait for your intervention.
Shutdown and switch off the computer
There is a specific set of steps that a user must follow to shut down the computer. Otherwise there maybe problems like the software or hardware can get corrupted. Always follow the steps outlined below.
When we click on the YES button a message will appear “Its Now Safe to Turn of Your Computer”. After seeing these messages press the power button to switch off the computer. Now switch off the UPS and stabilizer and last but not least, switch off the wall socket i.e. the main power supply. As highlighted above, I have tried to explain the basics of personal computing skills. The computer works on binary system. While sending input, we use input device. In this case, we use Mouse and Keyboard. We send message in the form of command which are duly processed in the computer by way of creating the digital electronic signal.

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Source by Kh. Atiar Rahman