Computer Architecture

Basic Hardware Components

Basic Hardware Components

Learning Outcome:

To describe basic computer architecture with reference to

  • Motherboard,
  • Central Processing Unit (CPU),
  • Arithmetic and Logic Unit (ALU)
  • Memory - RAM and ROM,
  • Data and Address Bus,
  • Input and Output,
  • External Storage
  • Units of Data Measure (Conversion)


A Motherboard is a PCB (Printed Circuit Board) with different hardware components on it.

It is the electrical conductor of the computer, responsible for distributing current and communication to/from the hardware components and chipset (CPU, RAM etc.).

The Motherboard is also known as the Planar board, MOBO, MB, Mainboard, System Board, Logic Board, Base Board and Backplane Board.

The picture shows some basic mother board components. The information you are required to know are given in the learning outcome.

For more information on the other parts, check out the following site:

Central Processing Unit (CPU) or Processor

The central processing unit (CPU), also called a processor, is located inside the computer case on the motherboard. It is sometimes called the brain of the computer, and its job is to carry out commands. Whenever you press a key, click the mouse, or start an application, you're sending instructions to the CPU.

The CPU is usually a two-inch ceramic square with a silicon chip located inside. The chip is usually about the size of a thumbnail. The CPU fits into the motherboard's processor (CPU) socket, which is covered by the heat sink, an object that absorbs heat from the CPU.

A processor's speed is measured in megahertz (MHz), or millions of instructions per second; and gigahertz (GHz), or billions of instructions per second. A faster processor can execute instructions more quickly. However, the actual speed of the computer depends on the speed of many different components—not just the processor.

Arithmetic and Logic Unit (ALU)

An arithmetic logic unit (ALU) is a digital circuit used to perform arithmetic and logic operations. Examples of arithmetic operations are addition, subtraction, multiplication, and division. Examples of logic operations are comparisons of values such as NOT, AND, and OR. It represents the fundamental building block of the central processing unit (CPU) of a computer.

Typically, the ALU has direct input and output access to the processor controller, main memory (random access memory or RAM in a personal computer), and input/output devices.

Memory - RAM (Random Access Memory)

RAM (also called the Main Memory) is your system's short-term memory or volatile memory. Whenever your computer performs calculations, it temporarily stores the data in the RAM until it is needed.

This volatile or short-term memory disappears when the computer is turned off.

RAM has both Read and Write functionality. Data can be read from it or written to it. Also, unlike the ROM, data stored in RAM can be easily changed.

RAM is measured in megabytes (MB) or gigabytes (GB). The more RAM you have, the more things your computer can do at the same time. If you don't have enough RAM, you may notice that your computer is sluggish when you have several programs open. Due to this, many people add extra RAM to their computers to improve performance.

Memory - ROM (Read Only Memory)

ROM, on the other hand, is a type of non-volatile memory where data has been prerecorded and contains the programming that helps the computer ‘boot up’.

Commonly referred to as Read Only Memory, ROM retains its contents even after the computer is turned off; that’s the reason a computer can be switched on in the first place.

ROM typically has Read functionality only. Stored data cannot be easily changed.

It is fair to say that if not for ROM, you wouldn’t ever be able to switch on your computer.

Data and Address Bus

A bus is a pathway for digital signals to rapidly move data. There are three internal buses associated with processors: the data bus (bi-directional; transfers data from processor to memory and vice-versa), address bus (uni-directional; only from processor to memory), and control bus. Together, these three make up the “system bus” or the Front Side Bus.

A system bus is a single computer bus that connects the major components of a computer system, combining the functions of a data bus to carry information, an address bus to determine where it should be sent, and a control bus to determine its operation.

CPU Reading from Memory

CPU Writing to Memory

In summary:

  • A bus is a collection of wires for transporting data from one part of a computer to another.
  • The data bus is used to transport data between memory and the processor. It is bi-directional because data can be sent in both directions between the processor and memory.
  • The address bus is used to specify memory address information. It is uni-directional because address information is always sent in one direction only from the processor to memory.

Input/ Output for Integrated Peripherals

I/O or Input - Output for Integrated Peripherals is a Motherboard’s built-in external connector. It is where the Mouse, keyboard, monitor, USB cable, Firewire, SPDIF, Audio jacks and other external devices are to be connected.

External Storage

In computing, external storage comprises devices that store information outside a computer. Such devices may be permanently attached to the computer, may be removable or may use removable media.

External Storage come in the form of Magnetic (Typical internal hard-drives), Optical (CD, DVD, Blu-Ray) or Solid State (Solid State Disk (SSD), thumb drives, SD cards). Solid State disks don't have moving parts.

The images represent some of the common external storage devices.

Units of Data Measure (Conversion)

Modern computers evolved from machines designed for doing calculations, so for most computers today, data is represented as numbers. The smallest unit of data in a computer is a bit, or binary digit, which can take on the value of either 0 or 1. A computer stores and processes all data using binary numbers that consist of these digits.

A single bit would be too simple to represent complex data, so we usually talk about data being represented as bytes instead. A byte is a unit of data made up of eight bits.

The table shows some of common units of data measure in computing.

Amount of Storage Required

Different types of data require different amounts of storage space. Take a look at the following table for some examples.

Kilobyte is usually written as kB but sometimes can also be represented as KB. kb is kilobit however.

The uppercase B is used to represent Byte while the lowercase b is used to represent bit.