Characteristics of Computer Generations

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1. Characteristics of computer generations32. Input and output devices53. Block diagram of computer104. Introduction of number system105. Parts of computer system116. Types of computer167. Software and its varieties188. Limitation of computer18


First Generation (1940-1956) Vacuum TubesThe first computers used vacuum tubes for circuitry andmagnetic drumsformemory, and were often enormous, taking up entire rooms. They were very expensive to operate and in addition to using a great deal of electricity, generated a lot of heat, which was often the cause of malfunctions.

First generation computers relied onmachine language, the lowest-level programming language understood by computers, to perform operations, and they could only solve one problem at a time. Input was based on punched cards and paper tape, and output was displayed on printouts.The UNIVAC andENIACcomputers are examples of first-generation computing devices. The UNIVAC was the first commercial computer delivered to a business client, the U.S. Census Bureau in 1951.

A UNIVAC computer at the Census Bureau.Image Source:United States Census BureauSecond Generation (1956-1963) TransistorsTransistorsreplaced vacuum tubes and ushered in the second generation of computers. The transistor was invented in 1947 but did not see widespread use in computers until the late 1950s. The transistor was far superior to the vacuum tube, allowing computers to become smaller, faster, cheaper, more energy-efficient and more reliable than their first-generation predecessors. Though the transistor still generated a great deal of heat that subjected the computer to damage, it was a vast improvement over the vacuum tube. Second-generation computers still relied on punched cards for input and printouts for output.Second-generation computers moved from crypticbinarymachine language to symbolic, orassembly, languages, which allowed programmers to specify instructions in words.High-level programming languageswere also being developed at this time, such as early versions ofCOBOLandFORTRAN. These were also the first computers that stored their instructions in their memory, which moved from a magnetic drum to magnetic core technology.The first computers of this generation were developed for the atomic energy industry.

Third Generation (1964-1971) Integrated CircuitsThe development of theintegrated circuitwas the hallmark of the third generation of computers. Transistors were miniaturized and placed onsiliconchips, calledsemiconductors, which drastically increased the speed and efficiency of computers.Instead of punched cards and printouts, users interacted with third generation computers throughkeyboardsandmonitorsandinterfacedwith anoperating system, which allowed the device to run many differentapplicationsat one time with a central program that monitored the memory. Computers for the first time became accessible to a mass audience because they were smaller and cheaper than their predecessors.Fourth Generation (1971-Present) MicroprocessorsThemicroprocessorbrought the fourth generation of computers, as thousands of integrated circuits were built onto a single silicon chip. What in the first generation filled an entire room could now fit in the palm of the hand. The Intel 4004 chip, developed in 1971, located all the components of the computerfrom thecentral processing unitand memory to input/output controlson a single chip.

In 1981IBMintroduced its first computer for the home user, and in 1984Appleintroduced the Macintosh. Microprocessors also moved out of the realm of desktop computers and into many areas of life as more and more everyday products began to use microprocessors.

As these small computers became more powerful, they could be linked together to form networks, which eventually led to the development of the Internet. Fourth generation computers also saw the development of GUIs, themouseandhandhelddevices.

Fifth Generation (Present and Beyond) Artificial IntelligenceFifth generation computing devices, based onartificial intelligence, are still in development, though there are some applications, such asvoice recognition, that are being used today. The use ofparallel processingand superconductors is helping to make artificial intelligence a reality.Quantum computationand molecular andnanotechnologywill radically change the face of computers in years to come. The goal of fifth-generation computing is to develop devices that respond tonatural languageinput and are capable of learning and self-organization.

INPUT AND OUTPUT DEVICESBefore a computer can process your data, you need some method toinputthe data into the machine. The device you use will depend on what form this data takes (be it text, sound, artwork, etc.).Similarly, after the computer has processed your data, you often need to produceoutputof the results. This output could be a display on the computer screen,hardcopyon printed pages, or even the audio playback of music you composed on the computer.The terms input and output are used both as verbs to describe the process of entering or displaying the data, and as nouns referring to the data itself entered into or displayed by the computer.Below we discuss the variety of peripheral devices used for computer input and output.INPUT DEVICESKeyboardThe computerkeyboardis used to enter text information into the computer, as when you type the contents of a report. The keyboard can also be used to type commands directing the computer to perform certain actions. Commands are typically chosen from an on-screen menu using a mouse, but there are often keyboard shortcuts for giving these same commands.

Pointing DevicesThe graphical user interfaces (GUIs) in use today require some kind of device for positioning the on-screen cursor. Typical pointing devices are: mouse, trackball, touch pad, trackpoint, graphics tablet, joystick, and touch screen.Pointing devices, such as a mouse, connected to the PC via aserial ports(old),PS/2mouse port (newer), orUSBport (newest). Older Macs used ADB to connect their mice, but all recent Macs useUSB(usually to a USB port right on the USB keyboard).MouseThemousepointing device sits on your work surface and is moved with your hand. In older mice, a ball in the bottom of the mouse rolls on the surface as you move the mouse, and internal rollers sense the ball movement and transmit the information to the computer via the cord of the mouse.The neweroptical mousedoes not use a rolling ball, but instead uses a light and a small optical sensor to detect the motion of the mouse by tracking a tiny image of the desk surface. Optical mice avoid the problem of a dirty mouse ball, which causes regular mice to roll unsmoothly if the mouse ball and internal rollers are not cleaned frequently. Two-button mouse with scroll wheelWireless Macintosh mouseTouch padMost laptop computers today have atouch padpointing device. You move the on-screen cursor by sliding your finger along the surface of the touch pad. The buttons are located below the pad, but most touch pads allow you to perform mouse clicks by tapping on the pad itself.

TrackpointSome sub-notebook computers (such as the IBM ThinkPad), which lack room for even a touch pad, incorporate atrackpoint, a small rubber projection embedded between the keys of the keyboard. The trackpoint acts like a little joystick that can be used to control the position of the on-screen cursor.TrackballThetrackballis sort of like an upside-down mouse, with the ball located on top. You use your fingers to roll the trackball, and internal rollers (similar to whats inside a mouse) sense the motion which is transmitted to the computer. Trackballs have the advantage over mice in that the body of the trackball remains stationary on your desk, so you dont need as much room to use the trackball. Early laptop computers often used trackballs (before superior touch pads came along).Trackballs have traditionally had the same problem as mice: dirty rollers can make their cursor control jumpy and unsmooth. But there are modern optical trackballs that dont have this problem because their designs eliminate the rollers.

JoysticksJoysticks and other game controllers can also be connected to a computer as pointing devices. They are generally used for playing games, and not for controlling the on-screen cursor in productivity software.Touch screenSome computers, especially small hand-held PDAs, have touch sensitive display screens. The user can make choices and press button images on the screen. You often use a stylus, which you hold like a pen, to write on the surface of a small touch screen.Graphics tabletA graphics tablet consists of an electronic writing area and a special pen that works with it. Graphics tablets allows artists to create graphical images with motions and actions similar to using more traditional drawing tools. The pen of the graphics tablet is pressure sensitive, so pressing harder or softer can result in brush strokes of different width (in an appropriate graphics program).

ScannersAscanneris a device that images a printed page or graphic by digitizing it, producing an image made of tiny pixels of different brightness and color values which are represented numerically and sent to the computer. Scanners scan graphics, but they can also scan pages of text which are then run through OCR (Optical Character Recognition) software that identifies the individual letter shapes and creates a text file of the page's contents.MicrophoneAmicrophonecan be attached to a computer to record sound (usually through a sound card input or circuitry built into the motherboard). The sound is digitizedturned into numbers that represent the original analog sound wavesand stored in the computer to later processing and playback.MIDI DevicesMIDI(Musical Instrument Digital Interface) is a system designed to transmit information between electronic musical instruments. A MIDI musical keyboard can be attached to a computer and allow a performer to play music that is captured by the computer system as a sequence of notes with the associated timing (instead of recording digitized sound waves).

OUTPUT DEVICESCRT MonitorThe traditional output device of a personal computer has been theCRT(Cathode Ray Tube) monitor. Just like a television set (an older one, anyway) the CRT monitor contains a large cathode ray tube that uses an electron beam of varying strength to paint a picture onto the color phosphorescent dots on the inside of the screen. CRT monitors are heavy and use more electrical power than flat panel displays, but they are preferred by some graphic artists for their accurate color rendition, and preferred by some gamers for faster response to rapidly changing graphics.

Ink Jet PrinterFor hardcopy (printed) output, you need some kind of printer attached to your computer (or available over a network). The most common type of printer for home systems is the colorink jetprinter. These printers form the image on the page by spraying tiny droplets of ink from the print head. The printer needs several colors of ink (cyan, yellow, magenta, and black) to make color images. Some photo-quality ink jet printers have more colors of ink.Laser PrinterAlaser printerproduces good quality images by the same technology that photocopiers use. A drum coated with photosensitive material is charged, then an image is written onto it by a laser (or LEDs) which makes those areas lose the charge. The drum then rolls throughtoner(tiny plastic particles of pigment) that are attracted to the charged areas of the drum. The toner is then deposited onto the paper, and then fused into the paper with heat.Sound OutputComputers also produce sound output, ranging from simple beeps alerting the user, to impressive game sound effects, to concert quality music. The circuitry to produce sound may be included on the motherboard, but high quality audio output from a PC usually requires asound cardin one of the expansion slots, connected to a set of good quality external speakers or headphones.BLOCK DIAGRAM OF COMPUTERAcomputercan process data, pictures, sound and graphics. They can solve highly complicated problems quickly and accurately. A computer as shown in Fig. performs basically five major computer operations or functions irrespective of their size and make. These are:1) it accepts data or instructions by way of input,2) it stores data,3) it can process data as required by the user,4) it gives results in the form of output, and5) it controls all operations inside a computer.

INTRODUCTION OF NUMBER SYSTEMHuman beings use a 10 based or decimal number system, possibly because we have tens fingers and ten toes. Computers use a 2 based or binary system because it can be represented easily in hardware by on-off, open-closed, charged-uncharged states. For example a capacitor in RAM memory can be charged or not charged. A charged state represents a 1 and an uncharged (or not fully charged) state represents a 0. Likewise data stored on a hard disk at the molecular level can be magnetically aligned in one pattern or its opposite. Each pattern represents a 1 or 0.Decimal numbers can be converted to binary numbers, and vice-versa. This is essential as humans work in decimals and computers work in binary. The pages in this menu look at how to use each system and how they relate to each other. A look is also taken at the octal (base 8) and hexadecimal (base 16) systems.There are three Scratch files attached to this page that demonstrate the decimal, binary and hexadecimal number systems.PARTS OF COMPUTER SYSTEMIf you use a desktop computer, you might already know that there isn't any single part called the "computer." A computer is really a system of many parts working together. The physical parts, which you can see and touch, are collectively calledhardware. (Software, on the other hand, refers to the instructions, or programs, that tell the hardware what to do.)The following illustration shows the most common hardware in a desktop computer system. Your system might look a little different, but it probably has most of these parts. A laptop computer has similar parts but combines them into a single, notebook-sized package.

Desktop computer systemLet's take a look at each of these parts.System unitThesystem unitis the core of a computer system. Usually it's a rectangular box placed on or underneath your desk. Inside this box are many electronic components that process information. The most important of these components is thecentral processing unit (CPU), ormicroprocessor, which acts as the "brain" of your computer. Another component israndom access memory (RAM), which temporarily stores information that the CPU uses while the computer is on. The information stored in RAM is erased when the computer is turned off.Almost every other part of your computer connects to the system unit using cables. The cables plug into specificports(openings), typically on the back of the system unit. Hardware that is not part of the system unit is sometimes called aperipheral deviceordevice.System unitStorageYour computer has one or moredisk drivesdevices that store information on a metal or plastic disk. The disk preserves the information even when your computer is turned off.Hard disk driveYour computer'shard disk drivestores information on ahard diska rigid platter or stack of platters with a magnetic surface. Because hard disks can hold massive amounts of information, they usually serve as your computer's primary means of storage, holding almost all of your programs and files. The hard disk drive is normally located inside the system unit.Hard disk driveCD and DVD drivesNearly all computers today come equipped with a CD or DVD drive, usually located on the front of the system unit. CD drives use lasers to read (retrieve) data from a CD; many CD drives can also write (record) data onto CDs. If you have a recordable disk drive, you can store copies of your files on blank CDs. You can also use a CD drive to play music CDs on your computer.CDDVD drives can do everything that CD drives can, plus read DVDs. If you have a DVD drive, you can watch movies on your computer. Many DVD drives can record data onto blank DVDs.MouseA mouse is a small device used to point to and select items on your computer screen. Although mice come in many shapes, the typical mouse does look a bit like an actual mouse. It's small, oblong, and connected to the system unit by a long wire that resembles a tail. Some newer mice are wireless.MouseKeyboardA keyboard is used mainly for typing text into your computer. Like the keyboard on a typewriter, it has keys for letters and numbers, but it also has special keys: Thefunction keys, found on the top row, perform different functions depending on where they are used. Thenumeric keypad, located on the right side of most keyboards, allows you to enter numbers quickly. Thenavigation keys, such as the arrow keys, allow you to move your position within a document or webpage.KeyboardMonitorAmonitordisplays information in visual form, using text and graphics. The portion of the monitor that displays the information is called thescreen. Like a television screen, a computer screen can show still or moving pictures.There are two basic types of monitors:CRT(cathode ray tube) monitors and the newerLCD(liquid crystal display) monitors. Both types produce sharp images, but LCD monitors have the advantage of being much thinner and lighter.

LCD monitor (left); CRT monitor (right)

PrinterA printer transfers data from a computer onto paper. You don't need a printer to use your computer, but having one allows you to print email, cards, invitations, announcements, and other material. Many people also like being able to print their own photos at home.The two main types of printers areinkjet printersandlaser printers. Inkjet printers are the most popular printers for the home. They can print in black and white or in full color and can produce high-quality photographs when used with special paper. Laser printers are faster and generally better able to handle heavy use.

Inkjet printer (left); laser printer (right)SpeakersSpeakers are used to play sound. They can be built into the system unit or connected with cables. Speakers allow you to listen to music and hear sound effects from your computer.

Computer speakersModemTo connect your computer to the Internet, you need amodem. A modem is a device that sends and receives computer information over a telephone line or high-speed cable. Modems are sometimes built into the system unit, but higher-speed modems are usually separate components.

Cable modemTYPES OF COMPUTERThetypes of computersrange from the Hybrid to the Analog types. The computers you come across in the daily course of your day range from laptops, palmtops and towers, to desktop computers, to name a few. But the very word "computers" reminds one of the desktop computers used in offices or homes. Different categories of computes have been devised in keeping with our varied needs.The Types Of Computers:Analog and Hybrid (classification based on operational principle)

Analog Computers:The analog computer is almost an extinct type of computer these days. It is different from a digital computer in respect that it can perform numerous mathematical operations simultaneously. It is also unique in terms of operation as it utilizes continuous variables for the purpose of mathematical computation. It utilizes mechanical, hydraulic, or electrical energy or operation. Hybrid computers:These types of computers are, as the name suggests, a combination of both Analog and Digital computers.Apart from this, computers are also categorized on the basis of physical structures and the purpose of their use. Based on Capacity, speed and reliability they can be divided into three categories of computers:

1. The Mainframe Computer:These are computers used by large organizations like meteorological surveys and statistical institutes for performing bulk mathematical computations. They are core computers which are used for desktop functions of over one hundred people simultaneously.2. The Microcomputer:These are the most frequently used computers better known by the name of "Personal computers". This is the type of computer meant for public use. Other than Desktop Computer the choice ranges as follows: Personal Digital Computer Tablet PC Towers Work Stations Laptops Hand Held Computer

3. The Mini computer:Mini computers like the mainframe computers are used by business organization. The difference being that it can support the simultaneous working of up to 100 users and is usually maintained in business organizations for the maintenance of accounts and finances.Analog Computers:Analog Computers and Digital computers are the two kinds of computers, the combination of which is responsible for the invention of the modern Hybrid computers.Digital Computers:Digital Computers are that kind of computing machines which work on the principle of binary mathematics. Digital computing machines when clubbed with Analog computers produce Hybrid computers. The digital systems work on the principle of binary mathematics. In binary mathematics all calculations are represented through "0" and "1".Mainframe Computer:Mainframes are computers that are the most bulky types and with the advancement of technology, they have almost become extinct. Computers are of three types - Mainframe computers, Minicomputers and Microcomputers. Mainframe computer systems can be called the predecessor of servers because they could actually support multi users though as efficiently as the servers. Usually, a main frame would occupy an entire room and could cost over million dollars.Minicomputers:Minicomputers, what exactly are they? If supercomputers and mainframes are considered to be the best in terms of mathematical operations then minicomputer systems succeed them. Previously,minicomputers were considered to be superior to personal systems. But these days, advancement intechnology has made minicomputers almost obsolete because the PCs today are highly advanced.Supercomputers:Supercomputers are one of the many types of modern computing machines which are capable of giving very speedy calculations. It is because of their high speed processing ability that Supercomputer systems are used in such works as animation graphics, weather forecasting, nuclear research work, petroleum research works, crypt analysis, molecular modeling and the likes. You must be wondering then what is the difference between a supercomputer and a mainframe computer system? While Mainframe machines are primarily used for a number of purposes, supercomputers are so designed to serve a singular purpose.

SOFTWARE AND ITS VARIETY Types of Computer Software

Designed to store data, a computer is able to function in different and desired ways only due to a number of software applications that empower it.Various types of computer software help it execute a variety of operations every day. Computer software is available in different forms and types.Classification of Computer SoftwareBroadly, computer software can be classified into three categories. One, system software is the most important component for running a system or computer. System software is also known as operating system which helps start a computer and works as a main platform in order to run any application. A number of operating systems are in vogue that empower systems globally. However, these operating systems have a category of server and personal computer operating systems.Customization vs Off-the-shelf softwareIn addition, any individual software package, which may fall into any of the above categories, can be either 'off-the-shelf' or custom-built. Both are different and address different levels of user demands. Applications such as ERP, CRM and BI, when implemented into any enterprise, are usually customized in order to make them gel with the business processes of that enterprise. It usually happens because of the scale and nature of a business.LIMITATIONS OF COMPUTERThe computercan outperform human beings in speed, memory and accuracy but stillthe computerhas limitations. There are following limitations of a computer.Programmed by human:Though computer is programmedto workefficiently, fast and accurately but it is programmed by human beings to do so. Without a program, computer is nothing. A program is a set ofinstructions. Computer only follows theseinstructions. If theinstructionsare not accuratethe workingof computer will not accurate.Thinking:The computercan not think itself. The concept ofartificial intelligenceshows thatthe computercan think. But still this concept is dependent on set ofinstructionsprovided by the human beings.Self Care:A Computer can not care itself like a human. A computer is dependent still to human beings for this purpose.Retrieval of memory:A computer can retrieve data very fast but this technique is linear. A human being's mind does not follow this rule. A human mind can think randomly which a computer machine can not.Feelings:One of the main limits inthe computeris of feeling. A computer can not feel about some like a human. A computer can not meet human in respect of relations.Human can feel, think and caring but a computer machine itself can not.A computer can not take place of human because computer is always dependent of human.