Computer Generations & Hierarchies

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Computer Generations
History of development of computers down the years is referred as Computer Generations. A generation refers to research and development done to improve the performance of computers. It also refers to the new technical breakthroughs and advancements in computers. A generation has significantly decreased the size of computers and increased the performance. With the increase in speed, power and memory and decrease in size, each generation has brought down the cost and to be available to the masses. First Generation

Time Frame: 1940-1956
The computers in the first generation used vacuum tubes for circuitry and magnetic drums for memory, and were huge in size, taking up entire rooms. A magnetic drum, , is a metal cylinder coated with magnetic iron-oxide material on which data and programs can be stored. These were once used as a primary storage device but have since been implemented as auxiliary storage devices. The tracks on the magnetic drum are referred as channels located around the circumference of the drum, forming adjacent circular bands that wind around the drum. A single drum can have up to 200 tracks. As the drum rotates at a speed of up to 3,000 rpm(rotations per minute), the device's read/write heads deposit magnetized spots on the drum during the write operation and then senses these spots during a read operation. This action is similar to that of a presently used magnetic tape or disk drive. They were very expensive to operate as they use a great deal of electricity, as a result generated a lot of heat, which was often the cause of malfunctions. First generation computers relied on machine language to perform operations, and they could only solve one problem at a time, also known as batch operation. Machine languages are the only languages understood by computers. While easily understood by computers, machine languages are almost impossible for humans to use because they consist entirely of numbers. Computer programmers, therefore, use either high level programming languages or an assembly language programming. An assembly language contains the same instructions as a machine language, but the instructions and variables have names instead of being just numbers. Every computer has its own unique machine language. Every program must be rewritten or recompiled, to run on different types of computers. Input was based on punch card and paper tapes, and output was displayed on printouts. The UNIVAC and ENIAC(Electronic Numerical Integrator And Computer) computers 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. Second Generation

Time Frame: Second Generation (1956-1963)
Transistors replaced vacuum tubes in the second generation of computers. A transistor is a device composed of semiconductor material that amplifies a signal or opens or closes a circuit. Invented in 1947 at Bell Labs, transistors later became the key component of all digital circuits, including computers. Today's latest microprocessor contains tens of millions of microscopic transistors. Prior to the invention of transistors, the digital circuits were composed of vacuum tubes, which had many problems in operations. They were much larger, required more energy, dissipated more heat, and were more subject to failures. Without the invention of transistors, computers as we know and operate it today would not be possible. Though the transistor was invented in 1947 it was used widespread in computers until the late 50s. 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 generated a great deal of heat that subjected the computer to damage, it was a vast improvement over the vacuum tube. The second-generation computers l relied on punched cards for input...
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