Central Processing Unit (CPU): The Brain of all Computer System

Central Processing Unit (CPU): The Brain of all Computer System

Central Processing Unit (CPU): The Brain of all Computer System

The CPU, which contains all the circuitry required to process input, store data, and output results, is the brain of a computer.

The CPU is constantly executing computer programmes that give it instructions on which data to process and in what order. We couldn't use a computer to run programmes without a CPU.

The Microprocessor CPU

Any microprocessor or microcomputer system's central processing unit (CPU) serves as the brain and, as a result, the health of the system depends on the CPU's proper performance. The microprocessor's main job is to retrieve, decode, and carry out memory-resident instructions. As a result, it has to be able to move information from external memory to its internal registers and vice versa. Additionally, it must function predictably, recognizing differences between operations contained inside instructions and any accompanying addresses of read/write memory locations, for instance. Additionally, a number of system maintenance chores must be completed, such as responding to interruptions from outside devices.

 A microprocessor CPU's primary components are:

  • Registers for storing addresses and data momentarily;
  • Arithmetic and logic operations are carried out by an arithmetic logic unit (ALU); and
  • a mechanism of controlling and timing system operations. 

CPU Function

A single very large scale integrated (VLSI) microprocessor chip performs the CPU's functions in a microprocessor system. Thousands of individual transistors can be connected to this chip. The read-only and read/write memory is also provided by semiconductor devices. Since each piece of data can be retrieved with equal ease regardless of its precise location inside the memory, both forms of memory formally provide random access. Despite this, the term 'RAM' has become synonymous with semi-conductor read/write memory.


For instance, a straightforward calculator software might command the CPU to add the two digits 2 and 2 and report the answer back.

Thanks to a control unit that can understand programme instructions and an Arithmetic Logic Unit (ALU) that can add numbers, the CPU can process those instructions with ease. In comparison to a simple calculator, the CPU can process far more sophisticated programmes when the control unit and ALU are integrated.

Inside the CPU

At the physical level, a CPU is an integrated circuit, sometimes referred to as a chip. Millions or billions of tiny electrical components are "integrated" into an integrated circuit, which then organizes them into circuits and packs everything into a small space.

The system's core elements (CPU, RAM, ROM, and I/O) are connected by a bus, a multiple-wire connection mechanism. There are three main buses: 

  1. Address Bus, which specifies memory locations
  2. Data Bus, which transports data between devices; 
  3. Control Bus, which sends timing and control signals to every component of the system.

Depending on the specific CPU used, the address bus and data bus may have more or fewer individual lines. There are just two possible basic states for signals on all lines, regardless of whether they are used for address, data, or control: logic 0 (low) or logic 1. (high). Binary numbers, which are a series of 1s and 0s, are used to represent data and addresses. These numbers can be found on the data bus and address bus, respectively.

An 8-bit data bus and a 16-bit address bus are frequently used by microprocessors created for control and instrumentation applications. The condition where all eight lines are at logic 1 corresponds to the greatest binary number that can exist on an 8-bit data bus. The binary number 11111111 represents the greatest value of data that can be present on the bus at any given time (or 255). In a similar vein, 1111111111111111 is the highest address that can be present on a 16-bit address bus (or 65 535). For a straightforward microprocessor of this kind, the whole set of data values and addresses is as follows:

Addresses 0000000000000000 to 111 Data 00000000 to 11111111


The layers of the CPU chip are visible:

While some of those levels are abstractions like gates and logic circuits, others are actual components like transistors and chips.

It's astonishing that we can combine ostensibly straightforward components, such as logic gates, to produce CPUs that drive sophisticated gadgets, such as our phones, laptops, and even self-driving cars.

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