NCERT Book Class 11 Computer Science Microprocessors and Memory Concepts

NCERT Class 11 Computer Science Microprocessors and Memory Concepts

Microprocessor

We studied that the Central processing unit processes data inside the computer. It

interprets all the instructions given to it and carries out these instructions. A

microprocessor is a Central Processing Unit (CPU) on a single chip. It is a multipurpose

programmable device constructed using Metal Oxide Semiconductor (MOS)

technology. In 1971 Intel Corporation fabricated the first microprocessor- 4004. It could

do only add and subtract operations and that too it could process only 4 bits at a time.

But Intel 4004 powered one of the first portable electronic calculators and since then the

microprocessor technology has come a long way. Today we have processors with which

can process upto 128 bits at a time at the speed of billion instructions per second.

Let us now have a look at the characteristics of microprocessors:

•  Instruction Set: It is the set of instructions that the microprocessor executes

• Word Length: The number of bits processed in a single instruction is called word

length or word size. The word size is directly proportional to the processing power

of the CPU. During the processing, the internal general purpose registers hold

data. So if internal registers can hold data upto 8 bits, the word length is 8 bits. If it

can process 16 bits at a time, then the internal registers can hold upto 16 bits at a

time and so on. Hence a 32 bit processor is about 4 times faster than an 8 bit

processor. Examples of word lengths are 16 bit, 32 bit, 64 bit. The terms 16-bit

CPU, 32-bit CPU, 64-bit CPU are used very often while talking about CPUs. Now

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