Basic concepts of Microprocessor (ALU, CU & Register)

The microprocessor is the computer’s brain, and it is responsible for all of its operations. It is a computer processor that combines all CPU (Central Processing Unit) functions into a single IC (Integrated Circuit) or a few ICs.

A microprocessor is an essential component of a computer’s architecture. Without it, you won’t be able to do anything about it.

It’s a programmable system that takes in data, performs arithmetic and logical operations on it, and then outputs the desired results.

A microprocessor, in simple terms, is a digital computer on a chip that can fetch instructions from memory, decode and execute them, and return results.

Clock speed in Microprocessor

The speed at which a computer’s central processing unit (CPU) retrieves and interprets instructions is determined by the processor clock speed. This allows your machine to complete more tasks in a shorter amount of time.

Clock speeds are calculated in gigahertz (GHz), with the higher the number, the faster the clock. As clock speeds became more difficult to increase, multi-core processors were designed to make CPUs run faster.

Faster clock speeds mean that tasks ordered by your CPU can be done faster, resulting in a more streamlined experience and less time waiting to interact with your favorite applications and programs.

Word length in Microprocessor

The maximum number of bits that a computer’s processor can accept as input is referred to as the processor’s word length. It is the number of bits that a computer CPU will process in a single pass.

It is determined by the size of the internal data bus, registers, and ALU, among other factors. At a time, an 8-bit microprocessor can process 8 bits of data. Depending on the type of microcomputer, the word length will vary from 4 to 64 bits.

CPU components and functions

Basic Microcomputer
Computer Architecture

1. Arithmetic Logic Unit

ALU is the abbreviation for “Arithmetic Logic Unit.” An ALU is an integrated circuit that performs arithmetic and logic operations within a CPU or GPU.

Addition, subtraction, and moving operations are examples of arithmetic instructions, while boolean comparisons such as AND, OR, XOR, and NOT are examples of logic instructions.

The ALU serves two primary purposes:

  • It is capable of performing both arithmetic and logical operations (decisions). The ALU is the place where calculations and decisions are taken.
  • It serves as a connection between primary and secondary memory. The ALU is used to share data between them.

2. Control Unit

The control unit is a component of the computer’s central processing unit (CPU) that directs the processor’s operation.

The Control Unit is responsible for instructing the computer’s memory, arithmetic/logic unit, and input and output devices on how to respond to the instructions sent to the processor.

It fetches internal program instructions from the main memory to the processor instruction register, and the control unit produces a control signal based on the contents of this register to supervise the execution of these instructions.

Control Unit operates by taking in data and converting it into control signals that are then sent to the central processor.

The CU has a number of functions:

  • It retrieves, decodes, and executes commands.
  • It sends out control signals to hardware.
  • it transfers data across the device.

3. Registers

Inside the CPU, registers are tiny volumes of high-speed memory. For various reasons, different processors have different numbers of registers.

The processor uses them to store small amounts of data that are required during processing, such as:

  • Store the address of the next to be executed instruction.
  • The already decoded instruction (current instruction).
  • The outcome of the calculations (result).


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by Rajesh Bhatt
Rajesh is an IT Lecturer with a keen interest in Technological Research over the world. He is equally passionate about Gadgets, Music & Travelling.

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