Computer Awareness Quiz: CPU, Motherboard and Computer Architecture

The correct answer is A, 8 bit. A microprocessor is named after the width of its data bus, that is, the number of bits it can carry in and out in a single operation. Here there are eight data lines, so eight bits move at a time and the chip is an 8-bit microprocessor; the Intel 8085 is the classic example, with eight data lines and sixteen address lines. B is wrong because the sixteen address lines decide only how much memory the processor can reach, which is two raised to the power sixteen, or 65,536 locations, and not the name of the processor. C is wrong because 20 address lines belong to the Intel 8086 family, which could address one megabyte, and address lines again do not fix the bit size. D is wrong because a 32-bit processor would need thirty-two data lines. The rule to remember is simple: data lines give the bit size, address lines give the memory capacity.

The correct answer is B, Nibble. A byte is made up of eight bits, so half a byte is four bits, and four bits together are called a nibble. The term matters in hexadecimal arithmetic, because one hexadecimal digit represents exactly one nibble, which is why four binary digits convert neatly into a single hexadecimal character. A is wrong because a byte is the full group of eight bits, not half of itself, and it is the unit in which file sizes and memory are measured. C is wrong because a bit, short for binary digit, is the smallest unit of data and holds only a 0 or a 1, so it is one-eighth of a byte rather than one-half. D is wrong because word size is the number of bits a particular processor handles in one operation, which may be 8, 16, 32 or 64 bits depending on the machine, and is not a fixed fraction of a byte.

The correct answer is C, ROM. Read Only Memory is the permanent or non-volatile memory of a computer: its contents are written once and survive when the power is switched off, which is why the BIOS firmware that starts the machine and runs the power-on self-test is stored in it. A is wrong because RAM, or Random Access Memory, is volatile temporary memory; everything in it is lost the moment power is removed, which is why unsaved work disappears in a power cut. B is wrong because a CD-ROM is an optical secondary storage medium that you insert and remove, not the permanent internal memory built into the machine; the question asks for the computer's own memory. D is wrong because the CPU is the processing unit and not a memory at all, although the registers inside it do store a few values while a calculation is running.

The correct answer is A, Cache Memory. Cache is a small quantity of very fast static RAM placed between the processor and main memory to hold the instructions and data most likely to be needed next, and of the options given it has the shortest access time; only the registers inside the processor itself are faster. Cache is graded as L1, L2 and L3, with L1 nearest the core and quickest. D is wrong because random access memory is the main memory and is slower than cache, which is the whole reason cache exists. B is wrong because magnetic bubble memory is an old non-volatile technology that stored data as tiny magnetised regions in a thin film and was far slower than semiconductor memory. C is wrong because magnetic core memory, built from tiny ferrite rings, was the main memory of second generation computers and had access times measured in microseconds rather than nanoseconds.

The correct answer is B, Arithmetic Logic Unit. The ALU is the part of the processor that actually does the work on data: addition, subtraction, multiplication and division on the arithmetic side, and comparison along with the logical operations AND, OR and NOT on the logic side. Results produced by the ALU are placed in the accumulator register. A is wrong because the control unit performs no calculation; it decodes each instruction and issues the timing and control signals that direct the other units, which is why it is called the nervous system of the computer. C is wrong because the memory unit only stores instructions and data and hands them over when asked. D is wrong because the input unit merely accepts data from devices such as the keyboard, mouse and scanner and converts it into a form the machine can use.

The correct answer is C, Program Counter. The program counter, sometimes called the instruction pointer, always holds the memory address of the next instruction the processor will fetch, and it is incremented automatically as each instruction is taken up so that execution moves forward in order; a jump or branch instruction works simply by loading a new value into it. A is wrong because the accumulator holds the operand and the result of the current arithmetic or logical operation, not an address. B is wrong because the instruction register holds the instruction that has already been fetched and is being decoded now, which is one step behind the program counter. D is wrong because the memory data register holds the data that has just been read from, or is about to be written to, a memory location, while its companion the memory address register holds that location's address.

The correct answer is B, John von Neumann. In 1945 John von Neumann described a design in which a computer's instructions and its data are both held in the same memory in the same binary form, so that the machine can be given a new task simply by loading a new program instead of being rewired. Almost every general purpose computer today follows this von Neumann architecture, whose opposite is the Harvard architecture with separate memories for instructions and data. A is wrong because Charles Babbage, the father of the computer, designed the Difference Engine and the Analytical Engine in the nineteenth century, long before stored programs in electronic memory. C is wrong because Alan Turing is remembered for the Turing machine, the Turing test and his codebreaking work, and is called the father of artificial intelligence. D is wrong because Blaise Pascal built the Pascaline, a mechanical adding machine, in 1642.

The correct answer is B, Address bus. The address bus carries only the address of the memory location or the input-output port that the processor wants to use, and that address always travels outwards from the processor to memory, never back; a bus that carries signals in one direction only is unidirectional. A is wrong because the data bus must be bidirectional: data travels from memory to the processor when a location is read and from the processor to memory when a location is written. C is wrong because the control bus carries signals in both directions, since read and write signals go out from the processor while interrupt and ready signals come in from devices. D is wrong because the system bus is the collective name for all three buses taken together, so it cannot be described as unidirectional as a whole. The number of lines in the address bus decides how much memory can be reached.

The correct answer is C, 65,536. Each address line can be either 0 or 1, so n address lines give two raised to the power n distinct combinations, and each combination is one memory address. Here n is 16, and two raised to the power sixteen is 65,536, which is 64 kilobytes of addressable space; the Intel 8085 with its sixteen address lines is exactly this case. A is wrong because 1,024 is two raised to the power ten and corresponds to only ten address lines. B is wrong because 4,096 is two raised to the power twelve and corresponds to twelve address lines. D is wrong because 1,048,576, or one megabyte, is two raised to the power twenty and corresponds to the twenty address lines of the Intel 8086. Memorising that two to the power ten is one kilo, twenty is one mega and thirty is one giga settles this family of questions quickly.

The correct answer is B, Intel 4004. Released by Intel in 1971, the 4004 put a complete central processing unit on a single chip for the first time in a commercial product and was a 4-bit processor, originally designed for a calculator. Its arrival is treated as the start of the fourth generation of computers, which is defined by very large scale integration and the microprocessor. A is wrong because the Intel 8085, an 8-bit chip with sixteen address lines, came later in the 1970s and is the processor most used in Indian engineering syllabi, which is why it is a tempting distractor. C is wrong because the Intel 8086 was the 16-bit processor of 1978 that began the x86 line used in personal computers. D is wrong because the Motorola 68000, a 16/32-bit processor of 1979, came almost a decade after the 4004.

The correct answer is C, CMOS battery. CMOS stands for complementary metal oxide semiconductor, and a small chip of that type on the motherboard stores the BIOS setup values such as the boot order, the date and the time. Because that chip is volatile, a coin-sized lithium cell, usually the CR2032, keeps it powered when the computer is switched off; when this cell fails, the machine forgets the time and the BIOS settings at every restart. A is wrong because the SMPS, or switched mode power supply, converts alternating mains current into the regulated direct current the board needs, and is not a battery. B is wrong because a UPS battery sits outside the cabinet and keeps the whole computer running during a power cut. D is wrong because cache memory needs no battery of its own; it is powered along with the processor and loses its contents when the machine is off.

The correct answer is B, RAM is volatile and ROM is non-volatile. Random Access Memory is the working memory in which the operating system, the running programs and the data in use are held, and everything in it is lost the moment the power supply stops, which is exactly what volatile means. Read Only Memory keeps its contents permanently without power, which is why the BIOS firmware that starts the machine is placed there. A is wrong because it treats ROM as volatile, which would make it impossible for a computer to know how to boot. C is wrong because it reverses the two properties, and this reversal is the most common trap set in such questions. D is wrong because RAM cannot be non-volatile; its two usual forms, dynamic RAM in the DIMM slots and static RAM used as cache, both need continuous power, and dynamic RAM even needs constant refreshing.