Introduction To Computer Architecture and Organization Part 1

Introduction To Computer Architecture and Organization is the definition of basic attributes of hardware components and their interconnections, in order to achieve certain specified goals in terms of functions and performance.

A computer system is composed of many parts, both hardware and software. At the heart of the computer is the processor, the hardware that executes the computer programs. The computer also has memory, often several different types in one system.

The memory is used to store programs while the processor is running them, as well as store the data that the programs are manipulating. The computer also has devices for storing data, or exchanging data with the outside world. These may allow the input of text via a keyboard, the display of information on a screen, or the movement of programs and data to or from a disk drive.

Processor (CPU)

A Central Processing Unit is also called a processor, central processor, or microprocessor. The processor is the most important part of a computer, the component around which everything else is centered. In essence, the processor is the computing part of the computer. It carries out all the important functions of a computer.

It receives instructions from both the hardware and active software and produces output accordingly. It stores all important programs like operating systems and application software. CPU also helps Input and output devices to communicate with each other. Owing to these features of CPU, it is often referred to as the brain of the computer.


Generally, a CPU has three components:

  • ALU (Arithmetic Logic Unit)
  • Control Unit
  • Memory or Storage Unit

Control Unit: It is the circuitry in the control unit, which makes use of electrical signals to instruct the computer system for executing already stored instructions. It takes instructions from memory and then decodes and executes these instructions. So, it controls and coordinates the functioning of all parts of the computer.

The Control Unit’s main task is to maintain and regulate the flow of information across the processor. It does not take part in processing and storing data.

ALU: It is the arithmetic logic unit, which performs arithmetic and logical functions. Arithmetic functions include addition, subtraction, multiplication division, and comparisons. Logical functions mainly include selecting, comparing, and merging the data. A CPU may contain more than one ALU. Furthermore, ALUs can be used for maintaining timers that help run the computer.

Memory or Storage Unit/ Registers: It is called Random access memory (RAM). It temporarily stores data, programs, and intermediate and final results of processing. So, it acts as a temporary storage area that holds the data temporarily, which is used to run the computer.

Types of CPU

CPUs are mostly manufactured by Intel and AMD, each of which manufactures its own types of CPUs. In modern times, there are lots of CPU types in the market. Some of the basic types of CPUs are described below:

Single Core CPU: Single Core is the oldest type of computer CPU, which was used in the 1970s. It has only one core to process different operations. It can start only one operation at a time; the CPU switches back and forth between different sets of data streams when more than one program runs. So, it is not suitable for multitasking as the performance will be reduced if more than one application runs. The performance of these CPUs is mainly dependent on the clock speed. It is still used in various devices, such as smartphones.

Dual Core CPU: As the name suggests, Dual Core CPU contains two cores in a single Integrated Circuit (IC). Although each core has its own controller and cache, they are linked together to work as a single unit and thus can perform faster than the single-core processors and can handle multitasking more efficiently than Single Core processors.

Quad Core CPU: This type of CPU comes with two dual-core processors in one integrated circuit (IC) or chip. So, a quad-core processor is a chip that contains four independent units called cores. These cores read and execute instructions of CPU. The cores can run multiple instructions simultaneously, thereby increases the overall speed for programs that are compatible with parallel processing.

Quad Core CPU uses a technology that allows four independent processing units (cores) to run in parallel on a single chip. Thus by integrating multiple cores in a single CPU, higher performance can be generated without boosting the clock speed.

However, the performance increases only when the computer’s software supports multiprocessing. The software which supports multiprocessing divides the processing load between multiple processors instead of using one processor at a time.

Basic System Architecture

The processor alone is incapable of successfully performing any tasks. It requires memory (for program and data storage), support logic, and at least one I/O device (“input/output device”) used to transfer data between the computer and the outside world. The basic computer system is shown



A bus is a physical group of signal lines that have a related function. Buses allow for the transfer of electrical signals between different parts of the computer system and thereby transfer information from one device to another.

For example, the data bus is the group of signal lines that carry data between the processor and the various subsystems that comprise the computer. The “width” of a bus is the number of signal lines dedicated to transferring information. For example, an 8-bit-wide bus transfers 8 bits of data in parallel.


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