Dale - Computer Science Illuminated 41

Dale - Computer Science Illuminated 41 - tronically...

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14 Chapter 1 The Big Picture Figure 1.6 A transistor, replacing the vacuum tube Courtesy of Dr. Andrew Wylie Second Generation (1959–1965) The advent of the transistor (for which John Bardeen, Walter H. Brattain, and William B. Shockley won a Nobel Prize) ushered in the second genera- tion of commercial computers. The transistor replaced the vacuum tube as the main component in the hardware. The transistor was smaller, more reliable, faster, more durable, and cheaper, as shown in Figure 1.6. The second generation also witnessed the advent of immediate-access memory. When accessing information from a drum, the CPU had to wait for the proper place to rotate under the read/write head. The second gener- ation used memory made from magnetic cores , tiny doughnut-shaped devices, each capable of storing one bit of information. These cores were strung together with wires to form cells, and cells were combined into a memory unit. Because the device was motionless and was accessed elec-
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Unformatted text preview: tronically, information was available instantly. The magnetic disk , a new auxiliary storage device, was also developed during the second generation. The magnetic disk is faster than magnetic tape because each data item can be accessed directly by referring to its location on the disk. Unlike a tape, which cannot access a piece of data without accessing everything on the tape that comes before it, a disk is organized so that each piece of data has its own location identifier called an address. The read-write heads of a magnetic disk can be sent directly to the specific location on the disk where the desired information is stored. Third Generation (1965–1971) In the second generation, transistors and other components for the computer were assembled by hand on printed circuit boards . The third generation is characterized by integrated circuits (IC), solid pieces of silicon that contained the transistors, other components, and their...
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