What are the five parts of the computer hardware system and what does each one do?

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What are the five parts of the computer hardware system and what does each one do?
RAM is one of the essential components of a computer. (Thinkstock Images/Comstock/Getty Images)

Although they may seem like a single complex device, modern computers actually consist of several different hardware parts, each fulfilling a distinct and necessary purpose. Without any of these five basic components, a computer would either not be able to work or be unable to perform any but the most basic functions.

Power supply unit

Like any other electrical device, a computer needs a reliable supply of power to function. As its name implies, the power supply unit does exactly that: it converts the standard alternating current you get from a wall socket to lower voltage direct current suitable for powering the computer's various components. The PSU resembles a metal box. On the end facing the outside of the computer, it has a connector for the power cable that plugs into the mains; depending on the model, it may also have an on-off switch. On the other end of the PSU is a bundle of cables, terminating in differently-shaped connectors that attach to other computer components.


The motherboard is a large printed circuit board to which all other computer components are connected, and through which those components communicate with each other. One of the chips built into the motherboard hosts the Basic Input / Output System, or BIOS, a list of basic settings required for the computer to boot up. Most modern motherboards include built-in controllers for video and audio, to allow the computer to perform basic functions such as word processing and browsing the Internet without need for separate graphics and sound cards.

Central processing unit

The central processing unit acts as the "brain" of the computer. Everything a computer does, from the basic functions of the operating system to more complex tasks such as graphic design, gaming or video rendering, is controlled by a program -- a set of instructions that tells the CPU what to do. Depending on the complexity of the task, some load may be shifted away from the CPU and placed on other computer components that are also capable of dealing with it, such as a stand-alone graphics card.

Random access memory

RAM is a type of memory where data used in the course of a computer's normal operation is temporarily stored, only to be completely wiped when the computer is restarted or shut down. For example, when you perform a simple copy and paste operation, the data you copied is stored in the RAM, as is the information required for a program's undo function to work. The more complex a program is, the more RAM it requires to work smoothly, with particularly intensive tasks requiring many gigabytes of it.

Hard drive

The hard drive is where all information that exists permanently on a computer is stored, from the operating system and installed programs to any personal files, such as images, sounds and documents. A computer may have more than one hard drive, increasing the amount of data it can store; external hard drives that can be connected to a computer through a USB port also exist.

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