computer knowledge

Computer

A computer is a programmable machine. Generally computer is an electronic device and specially used for read, write, and compute, it is commonly operated machine and particular used for trade, education, and research.  The two principal characteristics of a computer are:

·         It responds to a specific set of instructions in a well-defined manner.

·         It can execute a prerecorded list of instructions (a program).

It is very reliable due to its certain characteristics like: Speed, Storage capacity, Accuracy, Flexible and unlimited resources, Versatility, Automation, and Diligence to do work. Modern computer are electronic and digital.

There are two components of computer

1.       Hardware: Hardware means the physical parts of the personal computer, such as motherboard, hard disk, RAM, CD-ROM.

2.       Software: It means programs of the computer, There are three types of software:

·         Application software: - word, excel, Photoshop, macromedia freehand, etc.

·         Utilities software: - Antivirus, WinZip, defragmenter etc.

·         System software: - windows 98, windows millennium, windows XP, windows Vista etc.

Basics of Hardware:

Ø  Device Driver: After adding any devices we need to install the software of the device to make work properly with the devices, that kind of software is called device driver. OR (simply it works as the bridge or interface between hardware devices and the software to control the specific devices.)

Ø  Device: There are two types of devices:

·         Internal devices (Input device): it means those type of devices which are add inside the cashing box at motherboard, especially in PCI Slots, IDE port, etc.

·         External devices (Output device): It means those types of devices which are add outside the cashing box, especially in USB parallel ports, serial ports, VGA ports, etc.

General computer input devices:

·         Keyboard: it is an input device consisting of set of typewriter-like keys that enable you to enter data into a computer. Computer keyboards are similar to electric-typewriter keyboards but contain additional keys. The keys on computer keyboards are often classified as follows:

Ø  Alphanumeric keys – letters and Numbers

Ø  Punctuation keys – commas, period, semicolon, and so on.

The standard layout of letters, numbers, and punctuation is known as a QWERTTY keyboard because the first five key on the top row or letters spell QWERTY.

·         Mouse: Mouse is a device that controls the movement of the cursor or pointer on a display screen. A mouse is a small object you can roll along a hard, flat surface. Its name is derived from its shape, which looks a bit like the mouse, its connecting wire that one can imagine to be a mouse’s tail.

·         Joysticks: A lever that moves in all directions and controls the movement of a pointer or come other display symbols. A joystick is similar to a mouse, except that with a mouse cursor stops moving as soon as you stop moving the mouse.  It is mostly used for computer games, but they are also used occasionally for CAD/CAM systems and other applications.

·         Scanners: It is an input device that can read test or illustrations printed on paper and translate the information into a form that the computer can use. Scanners differ from one another in the following respects:

Ø  Scanning technology

Ø  Resolution

Ø  Bit depth

Ø  Size and shape

·         Digital camera: images can be input into a computer using a digital camera. These images can then be manipulated in many ways using the various imaging tools available.

·         Digitizing tablet: it is an input device that enables you to enter drawings and sketches into a computer. It consists of an electronic tablet and cursor or pen.

·         Mouse pad: it is a pad over which you can move a mouse. Mouse pads provide more traction than smooth surfaces such as glass and wood, so they make it easier to move a mouse accurately.

Special computer input devices:

·         Touch screens: In touch screens, users have to press (touch) areas on the screen to pass data. A typical usage of the Touch Screen technology is some Bank ATM machines.

·         Magnetic Ink Character Recognition (MICR): it allows the computer to recognize characters printed using magnetic ink. MICR is a direct-entry method used in banks. This technology is used to automatically read those frustrating-looking numbers on the bottom of the cheque.

·         Speech input device: Speech or voice input devices convert a person’s speech into digital form. These input devices, when combined with appropriate software, form voice recognition systems. These systems enable users to operate microcomputers using voice commands.

·         Smart cards: This input device stores data in a microprocessor embedded in the card. This allows information, which can be updated, to be stored on the card. This method is used in Store cards which accumulate points for the purchaser, and to store phone numbers for cellular phones.

·         Light Pen:a light pen is a pointing device shaped like a pen and is connected to a VDU. The tip of the light pen contains a light sensitive element which, when placed against the screen, detects the light from the screen enabling the computer to identify the location of the pen on the screen. It has the advantage of ‘drawing’ directly onto the screen, but this can become uncomfortable, and they are not as accurate as digitizing tablets.

·         OCR (Optical Character Recognition): it is designed to translate images of typewritten text (usually captured by a scanner) into machine-editable text, or to translate pictures of characters into a standard encoding scheme representing them in (ASCII or Unicode). OCR began as a field of research in artificial intelligence and machine vision. Though academic research in the field continues, the focus on OCR has shifted to implementation of proven techniques.

·         Optical Mark Reader (OMR): OMR can read information in the form of numbers or letters and put it into the computer. The marks have to be precisely located as in multiple choice test papers.

·         Bar Code Reader: it provides a quick method of recording the sale of items. A bar code is a pattern printed in lines of different lines of differing thickness. The system gives fast and error-free entry of information into the computer.

Computer output devices

These are the components that have been used to receive the output of processed data. The output could be a picture displayed in the screen, printed document or the song played. Most of the computer output devices are common to home or office environment. However, there are devices that are not commonly available.

General computer output devices:

1.       Monitor: most of you may call this as “Computer Screen”. Monitors are in different sizes and types. Average size of monitor used in a home environment is from 15” – 21”. However there are large specially made monitors have been used for special purposes, such as Architecture designing, production designing etc. having a quality monitor is not enough to get a quality output. It is important to have a quality Video card (graphic card) installed in your PC. More information of your video cards can be found in computer hardware components page.

2.       Printers (printed copy): we all use printers. There are different types of printers such as Laser. This is the highest quality of printers among all type of printers. These printers are expensive than other printers. Laser printers are useful in office environment where speed and high quality is important.

Ø  Inkjet: These are good for low volume home use. These printers are using cartridges filled with ink to produce the printouts. Relatively slow in printing (around 4-6 pages per minute)

Ø  Dot-matrix: This is very old type of printer. They are ribbons. Quality is not very good. Useful for low quality printing.

Ø  Thermal: These printers do imaged based printing. Usually they have been used to print plastic cards, labels etc. It is important to buy the most suitable printer for your requirement.

3.       Speakers (sound): 
    it is important to have quality sound card in order to get the best output from your speakers.

4.       Line printers: These are high-speed printers capable of printing an entire line at one time. A fast line printer can print as many as 3000 lines per minute. The disadvantages of line printers are that they can print only on font, they cannot print graphics, the print quality is low, and they are very noisy.

5.       LCD and LED printers: These are similar to laser printer but uses piqued crystals or light emitting diodes rather than a laser to produce an image on the drum.

6.       Plotter: it is a device that draws pictures on paper based on commands form a computer. Plotters differ from printers in that they draw lines using a pen. In general, plotters are considerably more expensive than printers.

Generations of Computer:

In 1960’s decade a convention was organized to clarify the generation of the computer by the compute scientists. At that time two main components of the computer Memory (Storage) and Processing devices were taken to divide the generation. Now, computers are defined in five generations.

S.N.	Generation	Time period	Processing Devices	Machine	Advantages/ Disadvantages
1.	First generation	1945-1956	Vacuum tube (Valve	ENIAC, EDVAC, EDSAC	Large in size. Slower in Performance. More heat generation.
2.	Second Generation	1956-1963	Transistors	LEO mark III, ATLAS, UNIVAC II, ICT 13000, IBM P4000	Smaller in Size. Good performance and low heat generation comparing previous generations.
3.	Third Generation	1964-1971	IC (Integrated  Circuit)	VAX 11/780, ICT 1900 series, IBM 360 series, UNIVAC 1108/9000 series	Good performance. Smaller size.
4.	Fourth Generation	1971 to present	LSIC, VLSIC, ULSIC	IBM PC, Apple Macintosh etc.	Very good performance. Very reliable.
5.	Fifth Generation	Present and Beyond	Chips		Artificial Intelligence (AI)

Types of computer:

1.       Microcomputer: The most familiar kind of computer is the microcomputer. In the past, microcomputers have been considered to be of two types – personal computers and Workstations

Ø  Personal computers (PCs): Until recently, PCs were desktop or portable machines. These machines ran comparatively easy to use applications software such as the word processors, spreadsheets, etc., they were usually easier to use and more affordable than workstations.

Ø  Workstations: Workstations are, again, until recently, expensive, powerful machines used by engineers, scientists and other professionals who processed a lot of data. People who need to run complex programs and display both work in progress and results graphically also use workstations.

2.       Portable Computers: Personal computing market is seeing the miniaturization phenomena. Now, computers are becoming smaller yet more powerful. One type of PC that is rapidly growing in popularity is the portable computer, which can be easily carried around. There are three categories of portable computers:

Ø  Laptops/Notebooks: Laptops may be either AC-powered or battery-powered, or both. These computers are ideal for users who have to work away from their offices.

Ø  Subnotebooks: These are for frequent flyers and life-on-the-road professionals. Subnotebook users give up a full display screen and keyboard in exchange for less weight. These computers fit easily into any briefcase. They typically have an external floppy disk drive and monochrome monitor, although of late color models are available.

Ø  Personal Digital Assistants (PDAs): PDAs are much smaller than the subnotebooks. They combine pen input, writing recognition, personal organizational tools, and communication capabilities in a very small package.

3.       Minicomputers: it is also known as mid-range commuters were first developed as special-purpose mainframe computers they were used, for instance, to control machines in a manufacturing unit. However, now they are widely used as general-purpose computers. Minicomputers work well in what are known as distributed Data Processing (DDP). That is, a company’s processing power is decentralized, or distributed across different computers.

4.       Super computers: These are the most powerful and faster of al computer system. Supercomputers are even faster than the mainframes. Supercomputers are being use in the complex scientific calculation and research project. The super computers are important innovation in the history of computer. They may be employed in massive data processing, solving very complex problems. Supercomputers are used in weather forecasting, rock launching, seismology, nuclear physics, weapon research and son the cost of these computer are very high (more than 15 million dollars).

5.       Mainframes: Mainframe computers can process several million program instructions per second. Large organizations rely on these room-size systems to handle large programs with lots of data. These are mainly used by insurance companies, banks, airline and railway reservation system, etc.

6.       Network Computer: These are computers with minimal memory, disk storage and processor power designed to connect to a network, specially the internet.