COMPUTER COMPENENTS

A computer system consists of mainly four basic units; namely input unit, storage unit, central processing unit and output unit. Central Processing unit further includes Arithmetic logic unit and control unit, as shown in the figure:. A computer performs five major operations or functions irrespective of its size and make. These are
• it accepts data or instructions as input,
• it stores data and instruction
• it processes data as per the instructions,
• it controls all operations inside a computer, and
• it gives results in the form of output.

Desktop Computer System

Contents  [hide]  1 Functional Units: 2 Memory 3 Input / Output Devices: 3.1 Input Devices 3.2 Scanner 3.3 Output Devices:

Functional Units:

a. Input Unit: This unit is used for entering data and programs into the computer system by the user for processing.

Basic Computer Organisation

b. Storage Unit: The storage unit is used for storing data and instructions before and after processing.

c. Output Unit: The output unit is used for storing the result as output produced by the computer after processing.

d. Processing: The task of performing operations like arithmetic and logical operations is called processing. The Central Processing Unit (CPU) takes data and instructions from the storage unit and makes all sorts of calculations based on the instructions given and the type of data provided. It is then sent back to the storage unit. CPU includes Arithmetic logic unit (ALU) and control unit (CU)

Computer Chip

• Arithmetic Logic Unit: All calculations and comparisons, based on the instructions provided, are carried out within the ALU. It performs arithmetic functions like addition, subtraction, multiplication, division and also logical operations like greater than, less than and equal to etc.

• Control Unit: Controlling of all operations like input, processing and output are performed by control unit. It takes care of step by step processing of all operations in side the computer.

Memory

Computer’s memory can be classified into two types; primary memory and secondary memory

RAM

a. Primary Memory can be further classified as RAM and ROM.

• RAM or 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.

ROM or 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.

b. Secondary Memory

RAM is volatile memory having a limited storage capacity. Secondary/auxiliary memory is storage other than the RAM. These include devices that are peripheral and are connected and controlled by the computer to enable permanent storage of programs and data.

• CD ROM

Secondary storage devices are of two types; magnetic and optical. Magnetic devices include hard disks and optical storage devices are CDs, DVDs, Pen drive, Zip drive etc.

• Hard Disk

Hard disks are made up of rigid material and are usually a stack of metal disks sealed in a box. The hard disk and the hard disk drive exist together as a unit and is a permanent part of the computer where data and programs are saved. These disks have storage capacities ranging from 1GB to 80 GB and more. Hard disks are rewritable.

• Compact Disk

Compact Disk (CD) is portable disk having data storage capacity between 650-700 MB. It can hold large amount of information such as music, full-motion videos, and text etc. CDs can be either read only or read write type.

CD Drive

• Digital Video Disk

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 television or the computer too. These are not rewritable.

Hard Disk

Input / Output Devices:

These devices are used to enter information and instructions into a computer for storage or processing and to deliver the processed data to a user. Input/Output devices are required for users to communicate with the computer. In simple terms, input devices bring information INTO the computer and output devices bring information OUT of a computer system. These input/output devices are also known as peripherals since they surround the CPU and memory of a computer system.

Input Devices

An input device is any device that provides input to a computer. There are many input devices, but the two most common ones are a keyboard and mouse. Every key you press on the keyboard and every movement or click you make with the mouse sends a specific input signal to the computer.

Keyboard

• Keyboard: The keyboard is very much like a standard typewriter keyboard with a few additional keys. The basic QWERTY layout of characters is maintained to make it easy to use the system. The additional keys are included to perform certain special functions. These are known as function keys that vary in number from keyboard to keyboard.

• Mouse: 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.

• Trackball: 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.

• Touchpad: A touch pad is a device for pointing (controlling input positioning) on a computer display screen. It is an alternative to the mouse. Originally incorporated in laptop computers, touch pads are also being made for use with desktop computers. A touch pad works by sensing the user’s finger movement and downward pressure. • Touch Screen: It allows the user to operate/make selections by simply touching the display screen. A display screen that is sensitive to the touch of a finger or stylus. Widely used on ATM machines, retail point-of-sale terminals, car navigation systems, medical monitors and industrial control panels.

Mouse

• Light Pen: Light pen is an input device that utilizes a light-sensitive detector to select objects on a display screen.

• Magnetic ink character recognition (MICR): MICR can identify character printed with a special ink that contains particles of magnetic material. This device particularly finds applications in banking industry.

• Optical mark recognition (OMR): 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 test.

• Bar code reader: Bar-code 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.

Light Pen

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. (Fig. 1.7)

Scanner

Output Devices:

Output device receives information from the CPU and presents it to the user in the desired from. The processed data, stored in the memory of the computer is sent to the output unit, which then converts it into a form that can be understood by the user. The output is usually produced in one of the two ways – on the display device, or on paper (hard copy).

•Monitor: is often used synonymously with “computer screen” or “display.” Monitor is an output device that resembles the television screen (fig. 1.8). It may use a Cathode Ray Tube (CRT) to display information. The monitor is associated with a keyboard for manual input of characters and displays the information as it is keyed in. It also displays the program or application output. Like the television, monitors are also available in different sizes. • Printer: Printers are used to produce paper (commonly known as hard copy) output. Based on the technology used, they can be classified as Impact or Non-impact printers.

Impact printers use the typewriting printing mechanism wherein a hammer strikes the paper through a ribbon in order to produce output. Dot-matrix and Character printers fall under this category.

Monitor

Non-impact printers do not touch the paper while printing. They use chemical, heat or electrical signals to etch the symbols on paper. Inkjet, Deskjet, Laser, Thermal printers fall under this category of printers.

• Plotter: Plotters are used to print graphical output on paper. It interprets computer commands and makes line drawings on paper using multi colored automated pens. It is capable of producing graphs, drawings, charts, maps etc. • 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.

Plotter

• Sound cards and Speaker(s): An expansion board that enables a computer to manipulate and output sounds. Sound cards are necessary for nearly all CD-ROMs 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.

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COMPUTER OF CLASSIFICATION

Computers differ based on their data processing abilities. They are classified according to purpose, data handling and functionality.

According to purpose, computers are either general purpose or specific purpose. General purpose computers are designed to perform a range of tasks.

They have the ability to store numerous programs, but lack in speed and efficiency. Specific purpose computers are designed to handle a specific problem or to perform a specific task. A set of instructions is built into the machine.

According to data handling, computers are analog, digital or hybrid. Analog computers work on the principle of measuring, in which the measurements obtained are translated into data. Modern analog computers usually employ electrical parameters, such as voltages, resistances or currents, to represent the quantities being manipulated. Such computers do not deal directly with the numbers. They measure continuous physical magnitudes. Digital computers are those that operate with information, numerical or otherwise, represented in a digital form. Such computers process data into a digital value (in 0s and 1s). They give the results with more accuracy and at a faster rate. Hybrid computers incorporate the measuring feature of an analog computer and counting feature of a digital computer. For computational purposes, these computers use analog components and for storage, digital memories are used.

According to functionality, computers are classified as :

Analog Computer 

 An analog computer (spelt analogue in British English) is a form of computer that uses continuous physical phenomena such as electrical, mechanical, or hydraulic quantities to model the problem being solved

Digital Computer

 A computer that performs calculations and logical operations with quantities represented as digits, usually in the binary number system

Hybrid Computer (Analog + Digital)

 A combination of computers those are capable of inputting and outputting in both digital and analog signals. A hybrid computer system setup offers a cost effective method of performing complex simulations.

 On the basis of Size

Super Computer

The fastest and most powerful type of computer Supercomputers are very expensive and are employed for specialized applications that require immense amounts of mathematical calculations. For example, weather forecasting requires a supercomputer. Other uses of supercomputers include animated graphics, fluid dynamic calculations, nuclear energy research, and petroleum exploration.

The chief difference between a supercomputer and a mainframe is that a supercomputer channels all its power into executing a few programs as fast as possible, whereas a mainframe uses its power to execute many programs concurrently.

Mainframe Computer

A very large and expensive computer capable of supporting hundreds, or even thousands, of users simultaneously. In the hierarchy that starts with a simple microprocessor (in watches, for example) at the bottom and moves to supercomputers at the top, mainframes are just below supercomputers. In some ways, mainframes are more powerful than supercomputers because they support more simultaneous programs. But supercomputers can execute a single program faster than a mainframe.

Mini Computer

A midsized computer. In size and power, minicomputers lie between workstations and mainframes. In the past decade, the distinction between large minicomputers and small mainframes has blurred, however, as has the distinction between small minicomputers and workstations. But in general, a minicomputer is a multiprocessing system capable of supporting from 4 to about 200 users simultaneously.

 Micro Computer or Personal Computer

 

• •     Desktop Computer: a personal or micro-mini computer sufficient to fit on a desk.
  •    Laptop Computer: a portable computer complete with an integrated screen and keyboard. It is generally smaller in size than a desktop computer and larger than a notebook computer.
  •     Palmtop Computer/Digital Diary /Notebook /PDAs: a hand-sized computer. Palmtops have no keyboard but the screen serves both as an input and output device.

Workstations

A terminal or desktop computer in a network. In this context, workstation is just a generic term for a user's machine (client machine) in contrast to a "server" or "mainframe."

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COMPUTER HISTORY AND GENERATIONS

HISTORY & GENERATIONS

Ever since the man thought of counting, he developed the concept of communications. His initial approach to accounting and data computations and their recording was with help of sticks, pebbles or lines on walls of caves.Then he moved towards counting using ten fingers of his hands, which probably is the basis of present decimal system

The earliest computing device, which was used by Egyptians as early as 450 B.C., is ABACUS. The Chinese version of ABACUS was a bead on wires counting frame, which is still much is use in south east asia, China and Japan.

The first desktop calculator machine, which is capable to perform various arithmetic operations, was developed as early as 1642, which was pioneered by French scientist BLAISE PASCAL (1623-1662). This calculating machine mainly consisted of gears and wheels for calculations and this machine could perform only two basic operations i.e. addition and subtraction.

A German mathematician GOTTFRIED LEIBNITZ worked on improving this machine i.e. Pascal's calculator for performing four basic arithmetic operations (+,-,x,/).

Charles Babbage designed the early computer called difference engine in the year 1822. Which could produce reliable tables. He improved this machine and came out with a new idea of Analytical Engine in 1833, which could perform the basic arithmetic functions, which is intended to be completely automatic. This machine used punch cards as input output devices for basic input and output. He is called as "FATHER OF COMPUTERS".

In 1920, LEONARDO TORES demonstrated a digital calculating machine in Paris.

The concept of punched cards which was used by BABBAGE as I/O media, was developed further by HARMAN HOLLERITH in the year 1889. He is the founder of present IBM (International Business Machine) company.

As the demand for punched cards machine increased, there was inadequacy of these machine for scientific computations and this demand led to the development of electro mechanical calculators known as MARK-1, which was the first automatic general purpose digital computer which was able to do three additions per second, for multiplication it took about four seconds and about if took Aiken eleven seconds for division. This machine was designed by Prof. HOWARD AIKEN of Hardward University. This was in 1944.

The first electronic computer, ENIAC (Electronic Numerical Integrator And Calculator) was designed in 1946. It has capability to perform about 5,000 calculations per second. This was a huge computer which occupied about 1,500 sq.ft and weighed about 50 tons.

After ENIAC the next development was an electronic computer which was based on JOHN VON NEUMANN'S concept of stored program named as EDVAC (Electronic Discreate Variable Automatic Computer) and this was in 1949.

Almost simultaneously with EDVAC of U.S.A, the EDSAC (Electronic Delay Automatic Calculator) was developed by British scientists. This machine was capable to do mathematical operations which are executed in matter of a few micro seconds.

Then came in 1951 the commercial version of stored program computer UNIVAC (Universal Automatic Computer), which was first digital computer.

GENERATIONS

The development of computers has followed difference steps in the technology used and these steps of technological differences are called as generations.

FIRST GENERATION (1945-1960):

The first generation of computer were those computers which use Vacuum Tubes or Valves technology. Almost all the early computer like ENIAC, EDVAC, EDSAC etc. were made a reality only by the invention of vacuum tube, which is a fragile glass device that can control and amplify electronic signals. In this computer they are using 18,000

vacuum tubes, 70,000 resisters, 10,000 capacitors and 60,000 switches. It took 150 kilo watt electric power and it produce large amount of heat. They were bulky and required large space. They had small primitive memories and no auxiliary storage.

SECOND GENERATION (1960-1965):

With the development of transistors and their use in circuits, magnetic core for memory storage, the vacuum tubes of first generation are replaced by transistors to arrive at second generation of computers. The size of transistors is much smaller when compared to vacuum tubes. They consumed less power generated less heat and are faster and reliable. William B Shickley, John Burdeen and Walter H Brattain are the scientists develop the transistors. They are working bell telephone, U.S.A. They got noble prize. The major advantage use of transistors was that the size of computer has come down as well as the power consumption. Even the cost of transistors is less in comparison with the cost of vacuum tubes, the cost of computer reduced drastically, they were more reliable then first generation computers. Fortran, cobol, snowbal, algol etc. like high level languages are developed in this generation. In this generation they are using magnetic tapes for storing.

THIRD GENERATION (1965-1975):

With the development of silicon chips. The third generation of computers came into existence. These computers used compact integrated circuits (IC's) of silicon chips in place of transistors. Each of these IC's consisted of large number of chips in very small packages. With these IC's coming into picture the size of computers, cost, heat generation and power consumption decreased to a great extent, speed and reliability increased as compared to previous generations. These machines used IC's with LSI (Large Scale Integration).

FOURTH GENERATION (FROM 1975):

The computers belonging to these generation used Integrated Circuits with VLSI (Very Large Scale Integration). These computers have high processing powers, low maintenance, high reliability and very low power consumption. These computer reduces the cost as well as the size of the computer.

FIFTH GENERATION:

These computers use optic fiber technology to handle Artificial Intelligence, expert systems, robotics etc. These computers have very high processing speeds and are more reliable.

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