Vacuum tubes were used as the main electronic component in which generation of computers?

The correct answer is B, Charles Babbage. He designed the Difference Engine and then the Analytical Engine, and the Analytical Engine contained the logical parts of a modern computer: a store for holding numbers, a mill for calculating, punched-card input and a printed output. He never finished building it, but the design is the reason he carries the title.

Option A, Blaise Pascal, built the Pascaline in 1642, the first mechanical adding machine, so he belongs to the earlier age of calculators rather than computers. Option C, Alan Turing, gave the theory of computation and the Turing machine and is called the father of computer science and of artificial intelligence, which is a different title from the one asked here. Option D, Herman Hollerith, built the punched-card tabulating machine used for the American census and founded the firm that later became IBM. Examiners rotate these four names in the options, so fix one phrase to each.

The correct answer is C, Bell Laboratories. John Bardeen, Walter Brattain and William Shockley demonstrated the transistor there in 1947, and the three shared the Nobel Prize in Physics for it. Because a transistor did the work of a vacuum tube while being far smaller, cooler and more reliable, it became the defining component of the second generation of computers.

Option A, Texas Instruments, is where Jack Kilby built the first integrated circuit in 1958, which belongs to the third generation, so it is the classic trap in this question. Option B, Intel Corporation, was founded much later and released the Intel 4004 microprocessor in 1971, opening the fourth generation. Option D, IBM Research, produced important second and third generation machines such as the IBM 1401 and the System 360, but it did not invent the transistor. Keep the pairs fixed: transistor with Bell Labs, integrated circuit with Texas Instruments, microprocessor with Intel.

The correct answer is D, UNIVAC-I, the Universal Automatic Computer. It was the first electronic computer built to be sold to customers rather than used only in a laboratory, and it was famously put to work on census and business data processing. It belongs to the first generation and used vacuum tubes.

Option A, ENIAC, the Electronic Numerical Integrator and Computer, was built by J. Presper Eckert and John Mauchly and is remembered as one of the first general-purpose electronic computers, but it was a one-off machine and not a commercial product. Option B, EDVAC, was its successor and is remembered for putting the stored program idea into practice. Option C, the Harvard Mark I, was an electro-mechanical machine driven by relays rather than a fully electronic computer. Papers deliberately place ENIAC first in the list, so read the word commercially with care.

The correct answer is B, 1971. The Intel 4004 placed an entire processing unit on a single chip for the first time in a commercial product, and that step marks the beginning of the fourth generation of computers, built on very large scale integration. Everything that followed, including the personal computer, rests on it.

Option A, 1964, is the year of the IBM System 360, a landmark third-generation machine built on integrated circuits, which is why the year appears as a distractor. Option C, 1975, is associated with the early hobby computers of the microprocessor era but not with the 4004 itself. Option D, 1981, is the year the IBM Personal Computer was launched, a fourth-generation product rather than the first microprocessor. The safe way to remember the chain is 1947 transistor, 1958 integrated circuit, 1971 microprocessor.

The correct answer is C, RAM. Random access memory holds the programs and data the processor is working on at that moment, and it is volatile: the instant the power supply is cut, everything stored in it disappears. That is why unsaved work is lost in a power failure.

Option A, ROM, is read-only memory, written normally at manufacture and non-volatile, so it keeps the start-up instructions safely when the machine is switched off. Option B, the hard disk, is secondary storage and is non-volatile by design, since its whole purpose is to hold data permanently. Option D, EPROM, is erasable programmable read-only memory, a ROM variant whose contents can be wiped with ultraviolet light and rewritten, but it too retains data without power. The single word to test in such a question is volatile, and only RAM carries it.