Hardware/Software & Input/Output Devices
1. Introduction. Components of computers
Computer components can be broadly divided into two categories:
It refers to physical component of a computer we can touch or see. For example, CPU, Monitor, Keyboard, Hard Disk, Floppy Disk, etc.
Types of Hardware
The hardware components of a microcomputer can be classified into the following types:
(b) Central Processing Unit or Processor
(c) Computer Memory and Mass Storage Devices
(f) Solid state backing storage
(c) Input Devices
(d) Output Devices
It also known as system board is the most important hardware component of a microcomputer. A motherboard contains the CPU chip, memory chip (ROM and RAM), I/O interface controller, expansion slots and many other logic circuits.
Motherboard include sound cards, video cards, network cards, hard drives, or other forms of persistent storage; TV tuner cards, cards providing extra USB or FireWire slots and a variety of other custom components.
Alternatively referred to as the brain of the computer, processor, central processor, or microprocessor, the CPU (pronounced as C-P-U), short for Central Processing Unit, was first developed at Intel with the help of Ted Hoff in the early 1970’s.
The computer CPU is responsible for handling all instructions it receives from hardware and software running on the computer.
c. Computer memory
Memory is used to store data and instructions. Computer memory is the storage space in computer where data is to be processed and instructions required for processing are stored. The memory is divided into large number of small parts called cells. Each location or cell has a unique address which varies from zero to memory size minus one.
Memory is primarily of three types
1. Primary Memory/Main Memory
2. Cache Memory
3. Secondary Memory
1. Primary Memory/Main Memory
Primary memory holds only those data and instructions on which computer is currently working. It has limited capacity and data is lost when power is switched off. The data and instruction required to be processed reside in main memory. It is divided into two subcategories RAM and ROM.
Two Types of Primary Memory are RAM & ROM
1. Random Access Memory (RAM). Random Access Memory is the unit in a computer system. It is the place in a computer where the operating system, application programs and the data in current use are kept temporarily so that they can be accessed by the computer’s processor. It is said to be ‘volatile’ since its contents are accessible only as long as the computer is on. The contents of RAM are no more available once the computer is turned off.
2. Read Only Memory (ROM). Read Only Memory is a special type of memory which can only be read and contents of which are not lost even when the computer is switched off. It typically contains manufacturer’s instructions. Among other things, ROM also stores an initial program called the ‘bootstrap loader’ whose function is to start the operation of computer system once the power is turned on.
2. Cache Memory
CACHE memories are accessed much faster than conventional RAM. It is used to store programs or data currently being executed or temporary data frequently used by the CPU. It is also very expensive to have bigger size of cache memory. Its size is therefore, normally kept small.
3. Secondary Memory
This type of memory is also known as external memory or nonvolatile. It is slower than main memory. These are used for storing data/Information permanently. CPU directly does not access these memories instead they are accessed via input/output routines. Contents of secondary memories are first transferred to main memory, and then CPU can access it.
Types of Secondary Memory
1. Magnetic Tape
Magnetic tapes are used for large computers like mainframe computers where large volume of data is stored for a longer time. The cost of storing data in tapes is inexpensive. Tapes consist of magnetic materials that store data permanently. Magnetic tapes are used for application which requires extremely large storage capacity where speed of access is not an issue. It is commonly used for backups of file servers for computer networks, in a variety of batch processing applications such as reading of bank cheques, payroll processing and general stock control
2. Magnetic Disk
Magnetic disks used in computer are made on the same principle. It rotates with very high speed inside the computer drive. Data is stored on both the surface of the disk. Magnetic disks are most popular for direct access storage device. Each disk consists of a number of invisible concentric circles called tracks. Information is recorded on tracks of a disk surface in the form of tiny magnetic spots. The presence of a magnetic spot represents one bit and its absence represents zero bit. The information stored in a disk can be read many times without affecting the stored data. So the reading operation is nondestructive. But if you want to write a new data, then the existing data is erased from the disk and new data is recorded. For Example Floppy Disk or Hard Disk Drives.
3. Optical Disk
With every new application and software there is greater demand for memory capacity. It is the necessity to store large volume of data that has led to the development of optical disk storage medium. Optical disks can be divided into the following categories:
(a) Compact Disk – Compact Disk (CD) is portable disk having data storage capacity between 650700MB. It can hold large amount of information such as music, fullmotion videos, and text etc. CDs can be either read only or read write type.
(b) DVD. DVDs are used to hold very large files (several GB) such as movie films. Digital Video Disk (DVD) is similar to a CD but has larger storage capacity and enormous clarity. Depending upon the disk type it can store several Gigabytes of data. DVDs are primarily used to store music or movies and can be played back on your televisión or the computer too. These are not re.writable.
(c) CD ROM / DVD ROM – Applications which require the prevention of deletion of data, accidental or otherwise. CDs used by software companies for distributing software programs and data; by Music companies for distributing music albums and by book publishers for distributing encyclopedias, reference books etc. DVDs used by film distributors.
(d) CD R/DVD R Applications which require a single ‘burning’ of data, e.g. CDs recording of music downloads from the Internet, recording of music from MP3 format, recording of data for archiving or backup purposes. DVDs – recording of film movies and television programs.
(e) CD RW/DVD RW - Applications which require the updating of information and ability to record over old data. Not suitable for music recording but is very useful for keeping generations of files. DVDs have between five and ten times the capacity of CDs.
d. Solid state backing storage
These are the smallest form of memory available in the market today. Widely used as removable storage. They are more robust than other forms of storage. Though expensive than other forms they can be easily written to an updated. For e.g. Pen drives & memory card or flash memory card.
1. Memory sticks/Pen drives - USB flash drives are typically removable and rewritable, much smaller than a floppy disk. Storage capacities typically range from 64 MB to 64 GB. Flash drives are widely used to transport files and backup data from computer to computer.
2. Flash memory cards – A memory card or flash memory card is a solid-state electronic flash memory data storage device used with digital cameras, handheld and Mobile computers, telephones, music players, video game consoles, and other electronics.
e. Input devices
Input devices accept data and instructions from the user.
Following are the examples of various input devices, which are connected to the computer for this purpose.
3. Light Pen
4. Optical/magnetic Scanner
5. Touch Screen
6. Microphone for voice as input
7. Track Ball
9. Bar codes
10. Digital camera
11. Magnetic ink character recognition (MICR)
13. Optical Mark Readers
A keyboard is the most common input device. The keyboard in most common use is the QWERTY board. Generally standard keyboard has 104 keys. Computer keyboards are QWERTY KEYBOARDS. The alphabetic keys are arranged so that the upper-left row of letters begins with the six letters Q W E R T Y.
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 and flat surface. Its name is derived from its shape, which looks a bit like a mouse. As you move the mouse, the pointer on the display screen moves in the same direction.
iii. Light pen
An input device that utilizes a lightsensitive detector to select objects on a display screen. A light pen is similar to a mouse, except that with a light pen you can move the pointer and select objects on the display screen by directly pointing to the objects with the pen.
iv. Optical Scanner
Scanner is an input device that can read text or illustration printed on paper and translates the information into a form that the computer can use. A scanner works by digitizing an image. It can scan typed documents, pictures, graphics or even handwriting into a computer. Photographs scanned into a microcomputer appear clearly on the screen and can be displayed whenever desired.
v. Touch Screen
It works whenever you touch any Touch Screen Device for example Latest Mobile, ATM, Kiosk machine, etc. Touch panel displays and pads are now being offered as alternatives to keyboard. Here the input can be given through the computer screen that accepts the input through monitor; users touch electronic buttons displayed on the screen or they may use light pen.
Microphone is an input device, which takes voice as input. The voice communication is more errorprone than information through keyboard. There are two types of microphones available
1. Desktop Microphone
2. Hand held Microphone
vii. Track Ball
A trackball is an input device used to enter motion data into computers or other electronic devices. It serves the same purpose as a mouse, but is designed with a moveable ball on the top, which can be rolled in any direction.
The joystick is a vertical stick which moves the graphic cursor in a direction the stick is moved. It typically has a button on top that is used to select the option pointed by the cursor. Joystick is used as an input device primarily used with video games, training simulators and controlling robots.
ix. Bar codes
A bar code is a set of lines of different thicknesses that represent a number. Barcode readers are photoelectric scanners that read the bar codes or vertical zebra strips marks, printed on product containers. These devices are generally used in super markets, bookshops etc
x. Digital camera
A digital camera can store many more pictures than an ordinary camera. Pictures taken using a digital camera are stored inside its memory and can be transferred to a computer by connecting the camera to it. A digital camera takes pictures by converting the light passing through the lens at the front into a digital image.
xi. Magnetic ink character recognition (MICR)
MICR is a characterrecognition technology used mainly by the banking industry to ease the processing and clearance of cheques and other documents. The MICR encoding called the MICR line, is at the bottom of cheques and other vouchers and typically includes the documenttype indicator, bank code, bank account number, cheque number, cheque amount, and a control indicator. The technology allows MICR readers to scan and read the information directly into a datacollection device. Unlike barcodes and similar technologies, MICR characters can be read easily by humans.
A joystick is a pointing device often used for playing games. The joystick has a gearshiftlike lever that is used to move the pointer on the screen. In industry and manufacturing, joysticks are used to control robots. Flight simulators and other training simulators also use joysticks.
xiii. Optical Mark Readers
Optical mark recognition, also called mark sense reader, is a technology where an OMR device senses the presence or absence of a mark, such as pencil mark. OMR is widely used in tests such as aptitude tests.
f. Output devices
Output devices return processed data that is information, back to the user. Some of the commonly used output devices are:
1. Monitor (Visual Display Unit)
4. Sound cards and Speaker
5. Facsimile (FAX)
Monitor is the most important output device because people interact with this device most intensively than others. Computer information is displayed, visually with a video adapter card and monitor. Information processed within the CPU, that needs to be visually displayed, is sent to video adapter. The video adapter converts information from the format used, in the same manner as a television displays information sent to it by a cable service.
Two basic types of monitors are used with microcomputers, which are as follows:
(a) Cathode Ray Tube (CRT)
Cathode Ray Tube Monitor is the typical monitor that you see on a desktop computer. It looks a lot like a television screen, and works the same way. This type uses a large vacuum tube, called cathode ray tube (CRT). The main components of a CRT terminal are the electron gun, the electron beam controlled by an electromagnetic field and a phosphor coated display screen. The electron gun emits an electron beam which is directed towards the phosphor coated display by the electromagnetic field in order to create an image.
(b) Liquid Crystal Displays (LCD)
These types of monitors are also known as flat panel monitor. Most of these employ liquid crystal displays (LCDs) to render images. The major advantage of LCD is the low energy consumption. These days LCD monitor are very popular. The CRT (Cathode Ray Tube) is replaced by liquid crystal to produce the image.
Printers are used for producing output on paper. After a document is created on the computer, it can be sent to a printer for a hard copy (Printout). Some printers offer special features such as colored and large page formats.
Plotters are used to print graphical output on paper. It interprets computer commands and makes line drawings on paper using multicoloured automated pens. It is capable of producing graphs, drawings, charts, maps etc.
iv. Sound cards and Speaker(s)
An expansion board that enables a computer to manipulate and output sounds. Sound cards are necessary for nearly all CDROMs and have become commonplace on modern personal computers. Sound cards enable the computer to output sound through speakers connected to the board, to record sound input from a microphone connected to the computer, and manipulate sound stored on a disk.
v. Facsimile (FAX)
Facsimile machine, a device that can send or receive pictures and text over a telephone line. Fax machines work by digitizing an image.
Computer software is the set of programs that makes the hardware perform a set of tasks in particular order. Hardware and software are complimentary to each other. Both have to work together to produce meaningful results. For example, DOS, Windows 2000/2003/XP/7, Linux , MSOffice Antivirus, All games etc.
Computer software is classified into two broad categories
1. Systems software
2. Application Software
1. Systems software
System software consists of a group of programs that control the operations of a computer equipment including functions like managing memory, managing peripherals, loading, storing, and is an interface between the application programs and the computer. MS DOS (Microsoft’s Disk Operating System), UNIX are examples of system software. There are four main jobs an operating system is responsible for:
1. It provides a user interface. The user interface lets you give commands to the OS.
2. It gives instructions to the computer hardware, such as the printer and monitor.
3. It manages the way in which the computer stores data and applications.
4. It keeps track of different jobs. For example, if you are using both a spreadsheet and a word processing application at the the same time, the OS will run both of these applications and let you switch back and forth between them.
2. Applications software
Software that can perform a specific task for the user, such as word processing, accounting, budgeting or payroll, fall under the category of application software. Word processors, spreadsheets, database management systems are all examples of general purpose application software.
Types of application software are:
(a) Word processing software: The main purpose of this software is to produce documents. MSWord, Word Pad, Notepad and some other text editors are some of the examples of word processing software.
(b) Database software: Database is a collection of related data. The purpose of this software is to organize and manage data. The advantage of this software is that you can change the way data is stored and displayed. MS access, dBase, FoxPro, Paradox, and Oracle are some of the examples of database software.
(c) Spread sheet software: The spread sheet software is used to maintain budget, financial statements, grade sheets, and sales records. The purpose of this software is organizing numbers. It also allows the users to perform simple or complex calculations on the numbers entered in rows and columns. MSExcel is one of the example of spreadsheet software.
(d) Presentation software: This software is used to display the information in the form of slide show. The three main functions of presentation software is editing that allows insertion and formatting of text, including graphics in the text and executing the slide shows. The best example for this type of application software is Microsoft PowerPoint.
(e) Multimedia software: Media players and real players are the examples of multimedia software. This software will allow the user to create audio and videos. The different forms of multimedia software are audio converters, players, burners, video encoders and decoders.
3. Utility software
Utility software may be considered as application software or system software which is very often used in the development of a programme. Examples of Utility softwares: WinZip, FrontPage, Notepad, Web Browsers etc. Below are some descriptions of utilities:
(a) Antivirus applications protect your computer from the damage that can be caused by viruses and similar programs.
(b) Compression utilities make files smaller for storage (or sending over the Internet) and then return them to normal size.
(c) Data recovery utilities attempt to restore data and files that have been damaged or accidentally deleted.
(d) Disk defragmenters reorganize the data stored on disks so that it is more efficiently arranged.
(e) Firewalls prevent outsiders from accessing your computer over a network such as the Internet.
4. Peripheral devices
Peripheral devices are connected to the computer externally. These devices are used for performing some specific functions.
Peripheral devices are all input devices and all output devices. They are described in the first pages of this document.