Input devices allow data to be entered into a computer. Output devices take information from a computer and convert it to a form understandable by humans. Below are some examples of each.

Input Devices	Output Devices
Keyboard	Monitor
Mouse	Printer
Touchscreen	Touchscreen
Microphone	Speaker
Camera	Light
(Barcode) scanner	Projector

Exam questions may ask for an appropriate input/output device to be recommended for a specific situation, with justification required for the choice made.

Random access memory (RAM) and read-only memory (ROM) are two types of primary storage - this is memory which the CPU can access quickly and directly.

Random Access Memory (RAM)	Read Only Memory (ROM)
Stores programs and data that is currently being used	Stores a computer's start-up instructions (boot program)
Volatile - loses contents when power is turned off	Non-volatile - retains contents when power is turned off
Can be read from and written to (could allow accidental or malicious changes to a piece of software)	Can only be read from (could prevent accidental or malicious changes)
Larger relative storage capacity (1-256 GB)	Smaller relative storage capacity (4-8 MB)

As RAM is volatile, and ROM can't be written to, somewhere is needed to store programs and data on a computer in the long-term while they are not in use and without needing a constant power supply. This is the role of secondary storage.

When an application is opened, it is loaded into the RAM from the secondary storage together with any needed data files. When the file/ changes are saved, they are transferred to the secondary storage from the RAM, and when the application is closed, it is removed from the RAM.

There are a number of different ways of storing information, including using magnetic, optical or flash technology.

• Magnetic storage uses tiny magnetised dots (particles); the magnetic state of each dot is used to represent binary information. These particles can be individually polarised to become either a north or south state, to represent either a 0 or 1.
• Hard Disk Drives (HDDs) work by magnetic patterns being read off platters that mechanically spin at high speeds.
• Optical storage works by burning sections of the surface of a disk using a laser, to create pits (bumps), and lands (flat areas). The data is written along a single track which spirals out from the centre of the disk. To read the data, a laser beam is shone onto the disk, and the reflected light is detected by a light sensor. Pits scatter light (so the light isn't reflected as well), which represents a 1, whereas lands reflect the light better, representing a 0.
• Optical storage typically comes in three different formats:
• Read-only (e.g CD-ROM), where the disk is written to during production and can then only be read from
• Recordable (e.g CD-R), where the disk can only be written to a single time
• Rewriteable (e.g CD-RW), where the disk can be written to multiple times
• Flash storage, or solid state storage, uses memory chips containing transistor gates to store data. These can have their contents erased and subsequently overwritten when an electrical charge is applied. An open gate allows current to flow when a voltage is applied, representing a 1, whereas a closed gate prevents current from flowing, representing a 0.

	Advantages	Disadvantages	Examples
Magnetic storage	Cheapest per bit of storage High data capacity Fast data access compared to optical	Moving parts mean it will eventually fail Slow data access compared to flash May be damaged by movement (not portable) Can be noisy due to moving parts	Hard Disk Drive (HDD) Magnetic tape Floppy disk
Optical storage	Cheap to produce and purchase Portable (makes distribution easy)	Prone to scratches (which permanently erase data) Low data capacity Slow data access	CD DVD Blu-ray
Flash storage	Very fast data access Low power consumption (as it has no moving parts) Quiet Portable (small, light and no moving parts)	Expensive There is a limited number of times that it can be written to	Solid State Drive (SSD) USB memory stick

Exam questions could ask for an appropriate storage device to be recommended for a specific situation, with justification required for the choice made.

Virtual storage describes the practice of storing information remotely, allowing it to be accessed by any computer with access to the same storage system (e.g over the internet). The information may appear to be stored locally (on your device), but it is actually physically located somewhere else, such as elsewhere on the network the device is connected to, or in the cloud using cloud storage services like Google Drive. Data may be stored across multiple different physical storage media, but is made by software to appear and act as if they are stored in a single location, to simplify the user experience.

Virtual storage on the cloud works by the user sending files over the internet to a data server, which then saves a copy. When the user then wants to access their file, the cloud storage provider allows the user to access the files on the server through a web-interface.

Advantages of virtual storage	Disadvantages of virtual storage
No need to purchase and install addition physical storage	If you have a slow connection, file access will be very slow
You can access your files from anywhere with a connection	You have to rely on someone else to keep your data secure
You can easily use & synchronise files across multiple devices	If you don't have a connection, you can't access your files