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 orig