There are four basic components of computer: 1. Input devices 2. Output devices 3. Data Processing and Control devices 4. Storage devices.Input devices gets input from the user. Examples of input devices are Keyboard, Barcode Reader,Joystick,MICR reader,OMR reader,OCR reader,Digital camera,Mouse,scanner,trackball,Light pen,Microphone,Touch screen and Punch cards.Output devices shows the output to the user.Examples of output devices are Monitor,plotter,Printer,Speaker and Projector.Central Processing Unit(CPU) performs data processing and controls the input,output and storage devices. Arithmetic and Logic unit(ALU) of CPU performs arithmetical and logical operations. Usually storage devices are embedded within CPU.
Important Input and Output devices:
Barcode reader reads barcode. Barcode is series of parallel lines. Specific information can be stored in a bacode by varying the distance between two lines, height and width of the line and this information is decoded by barcode reader.
Optical Mark recognition(OMR) scanner reads the answers shaded in the OMR sheet. The contrasting color used in shading answers help OMR scanner in reading the answer.
Optical Character recognition(OCR) scanner recognizes the manually written text.OCR scanner does so by pattern recognition.
Magnetic Ink Character recognition(MICR) scanner are used to read details of a cheque automatically. Refer MICR in this article for more information.
Printers prints text. Printing technology has evolved a lot since its first usage. Lets discuss the types of printers in the following passage. Dot matrix Printer is impact printer. They print character by the impact of pin against ink ribbon. Each impact produces a dot and the combination of many impacts produces a character. They can print 50-500 characters per second and they have very low print quality so that characters are barely visible. They can print multiple pages at a same time. This feature is not possible in Laser and Inkjet printers. Inkjet printer prints text and images by spraying ink on the paper. Color printing is also possible with Inkjet printers. Their print quality is as high as 300 dots per inch. Laser printers works on the same principle of Xerox machine. Laser Printer prints by passing laser light repeatedly.Laser Printer can print text and images with quality up to 2400 dots per inch. Thermal Printers prints text and image by applying heat to the heat sensitive paper through thermal pins.They produce low quality prints. LCD/LED printer prints by using liquid crystal or light emitting diodes. note: Only dot matrix printers are impact printers while other printers discussed here are non impact printers.
They are two major types of storage devices 1.Primary storage devices 2.Secondary storage devices
Common primary storage devices are Random Access memory(RAM),Read only memory(ROM), Programmable Read only memory(PROM), Erasable Programmable Read only memory(EPROM), Electrically Erasable Programmable Read only memory(EEPROM),Cache memory and registers. RAM is used to retain data in current session. Data stored in RAM is lost once the system is switched off and hence they are volatile in nature. ROM, PROM stores BIOS data and other critical data and hence they cannot be deleted. EPROM data can be deleted by passing Ultra violent rays. EEPROM data can be deleted by passing electrical signals. Magnetic tape,Hard disk,Floppy disk and Compact disk are commonly used secondary storage devices. Cache and register memory has high access speed and are used to handle data quickly. Secondary storage devices’ access speed are usually slower than that of primary storage devices. Secondary storage devices are cheaper than primary storage devices. Capacity of 3.5 inch Floppy disk is 1.44 MB. Capacity of CD is 700 MB. Capacity of DVD is 4.7 GB. Magnetic tape can access data only in serial order. CD ROM is non volatile and hence data stored in CD ROM cannot be edited and can only be read.