top of page

1.2 Computer Components

Exam Board:



2016 - Unit 1 

This page describe the various components inside of computer systems. The first three are necessary in every type of computer:



Power Supply Unit

A processor's main role is to manage the functions of a computer system by processing data and instructions


The primary processor of each computer system is the Central Processing Unit (CPU).

The motherboard is the main circuit board of a computer on which components such as the CPU and ROM are connected.

The motherboard contains PCI slots for expansion cards and ports for external devices.

The power supply unit (PSU) converts electricity from AC (Alternating Current) from the mains power supply to DC (Direct Current) which the computer system can use

The PSU of desktop computers is internal whereas portable devices require an external 'charger'.

CPU Diagram.png


Memory is split into two types - volatile and non-volatile.


  • Volatile storage is temporary (data is lost whenever the power is turned off).

  • Non-volatile storage saves the data even when not being powered, so it can be accessed when the computer is next on and can be stored long-term.

Random Access Memory (RAM)

Memory (ROM)

Cache Memory

RAM is volatile (temporary) storage that stores all programs that are currently running. RAM also stores parts of the operating system to be accessed by the CPU.

RAM is made up of a large number of storage locations, each can be identified by a unique address.

ROM is non-volatile storage that cannot be changed.

ROM stores the boot program / BIOS for when the computer is switched on. The BIOS then loads up the operating system to take over managing the computer.

Cache memory is volatile (temporary) storage that stores data that is frequently accessed.


It is very quick to access because it is closer to the CPU than other types of memory like RAM.


(Random Access Memory)

RAM (1).png


(Read Only Memory)


Cache Memory

Secondary Storage

Magnetic Storage

Optical Storage

Optical Storage Characteristics: 

X Low CAPACITY: 700 MB (CD), 4.7 GB (DVD), 25 GB (Blu-ray).

X - Not DURABLE because discs are very fragile and can break  or scratch easily.

 Discs are thin and very PORTABLE.

X Optical discs have the Slowest ACCESS SPEED.

Magnetic Disks are spelled with a k and Optical Discs have a c.

Magnetic Storage Characteristics: 

- Large CAPACITY and cheaper per gigabyte than solid state.

X - Not DURABLE and not very PORTABLE when powered on because moving it can damage the device.

✓ - Relatively quick ACCESS SPEED but slower than Solid State.

Optical storage uses a laser to project beams of light onto a spinning disc, allowing it to read data from a CD, DVD or Blu-Ray

This makes optical storage the slowest of the four types of secondary storage.

Disc drives are traditionally internal but external disc drives can be bought for devices like laptops.

A magnetic hard disk drive (HDD) is the most common form of secondary storage within desktop computers. A read/write head moves nanometres above the disk platter and uses the magnetic field of the platter to read or edit data. Hard disk drives can also be external and connected through a USB port.


An obsolete (no longer used) type of magnetic storage is a floppy disk but these have been replaced by solid state devices such as USB sticks which are much faster and have a much higher capacity. 


Another type of magnetic storage that is still used is magnetic tape. Magnetic tape has a high storage capacity but data has to be accessed in order (serial access) so it is generally only used by companies to back up or archive large amounts of data.

Solid State Storage

Cloud Storage

When you store data in 'the cloud', using services such as Google Drive or Dropbox, your data is stored on large servers owned by the hosting company. The hosting company (such as Google) is responsible for keeping the servers running and making your data accessible on the internet.

Cloud storage is typically free for a certain amount of storage. For example, as of 2019, Dropbox allow 2 GB for free or 2 TB for £9.99 a month.

Cloud storage is very convenient as it allows people to work on a file at the same time and it can be accessed from different devices. However, if the internet connection fails, or the servers are attacked then the data could become inaccessible.

There are no moving parts in solid state storage.


SSDs (Solid State Drives) are replacing magnetic HDDs (Hard DIsk Drives) in modern computers and video game consoles because they are generally quieter, faster and use less power.  

A USB flash drive (USB stick) is another type of solid state storage that is used to transport files easily because of its small size.

Memory cards, like the SD card in a digital camera or a Micro SD card in a smartphone, are another example of solid state storage.

Solid State Characteristics: 

X High CAPACITY but more expensive per gigabyte than magnetic.

Usually DURABLE but cheap USB sticks can snap or break

The small size of USB sticks and memory cards mean they are very PORTABLE and can fit easily in a bag or pocket.

Solid State storage has the fastest ACCESS SPEED because they contain no moving parts.

Cloud Storage Characteristics: 

- Huge CAPACITY and you can upgrade your subscription if you need more storage.

 / X - Cloud storage is difficult to rank in terms of PORTABILITY, DURABILITY and ACCESS SPEED because it depends on your internet connection. A fast connection would mean that cloud storage is very portable (can be accessed on a smartphone or tablet) but a poor connection would make access difficult.

Storage Protocols

SCSI (Small Computer System Interface) is a protocol (set of rules) for attaching external devices to a computer system, such as a printer, storage drive or scanner.

SAS (Serial Attached SCSI) is an improved version of SCSI that enables many more external devices (up to 128) to be connected at the same time to a computer system.

Expansion Cards

Expansion cards (dedicated circuit boards) have a specific purpose and are attached to the motherboard.

Most of the following expansion cards can also exist as integrated components on the motherboard, rather than a separate card.

Graphics Card

Sound Card

American Football Player

Processes graphical data (e.g. videos or animations) and converts it into a displayable output on a monitor.

Network Interface Card (NIC)

Sound Card.png

0010 1011 0101 0101 0110 0111 0101 0001 0101

Sound cards convert analogue sound waves into digital data (binary) when inputting audio through a microphone.​

Sound cards also convert digital data (binary) into analogue sound waves to output audio through speakers or headphones.

Sound Card.png

0010 1011 0101 0101 0110 0111 0101 0001 0101

Allows computers to connect to networks (such as the Internet) and enables them to transfer data to other computers.

Transfers data between servers across a network.


Fibre channel allows for quick transfer speeds and is primarily used to connect data storage to servers in large data centres.

Fibre Channel Card

Storage Controller Card

Required for the computer to manage and use any attached storage devices.


A port is the interface between external devices and the computer. Ports allow data to be transferred from and to these devices.

USB Port

USB Diagram.png

Connects storage devices such as USB sticks or external hard drives. Connects input devices such as a keyboard or mouse, as well as other devices for data transfer such as a camera or smartphone.

Ethernet Port

Ethernet Icon.png

Connects computers to network devices such as a modem or router, allowing access to the internet.

Firewire Port

Firewire Icon.png

Similar to USB but developed for Apple products, Firewire transfers data at a high speed from devices such as camcorders and external hard drives.


SATA Icon.png

Allows data transfer to external HDD, SSD or optical drives.

SD Icon.png

SD Port

Enables data from an SD card to be transferred from a device like a camera to the computer. 

Micro SD Port

Micro SD Icon.png

Allows data from a micro SD card to be transferred from devices such as smartphones, tablets and handheld games consoles to a computer.

Monochrome on Transparent.png

Questo's Questions

1.2 - Computer Components:

Vital Components: 

1. Describe the purpose of the following components:

  • a. The CPU (Central Processing Unit) [2]

  • b. The motherboard [2]

  • c. The PSU (Power Supply Unit) [2]

Primary Memory: 

2a. What is the difference between primary and secondary memory[2]

2b. What is the difference between volatile and non-volatile storage[2]

2c. For each of the three types of primary memory, describe its role and give an example of what it can store. [6]

Secondary Storage:

3a. For magnetic, optical and solid-state storage rank these three secondary storage mediums in terms of capacity, durability, portability and speed[9]

3b. For the following scenarios justify which secondary storage medium should be used and why it is the most appropriate:

  1. Sending videos and pictures to family in Australia through the post. [3]

  2. Storing a presentation to take into work. [3]

  3. Storing project files with other members of a group to work on together. [3]

  4. Backing up an old computer with thousands of file to a storage device. [3]


Additional Components:

4a. State the purpose of five different expansion cards[5]

4b. What is the purpose of the motherboard[2]


5a. Describe the six different ports[6]

5b. What is the difference between SCSI and SAS[2]

bottom of page