• Stack of disks, called platters, coated in a magnetic material.

• Effectively billions of tiny magnets, north = 1 and south = 0.

• The platters rotate and a set of sensors (heads) move across the platters sensing the change of north/south alignment of the magnets.

• Magnetic drives have a delay (latency) in accessing data because the head needs to move across the platter, SSD do not have moving parts, reducing the latency.

• The lack of moving parts also means the power consumption is lower and there is no heat or noise.

• SSD's do not experience slow speeds due to data fragmentation.

• SSD's are smaller and lighter, allowing more portable devices.

• SSD's are more robust as they are not as affected by shocks.

• Lasers are used to write and read the data.

• The surface of the disk is covered in billions of indentations.

• When the light is shone on the disk the indentations will reflect differently depending on whether is hits an indentation or not.

• This difference in the reflected light is interpreted as either a 1 or a 0 to represent binary data.

• Files and applications can be accessed from anywhere in the world with an internet connection.

• Applications are kept up to date without the user having to update anything themselves.

• Reduces the workload for network managers and technical support staff.

• Storage space is flexible, users can buy more storage as they need it.

• Improved security, the hosting company is responsible for keeping users data backed up.

• Sharing files with others is easier.

• Can only access files whilst there is an internet connection.

• Users no longer control the security of their files. Hackers more likely to attack a hosting company with many users data than an individuals computer system.

• Not always clear who owns the data (read about Facebook's terms and conditions).

• Hosting companies may change their terms and conditions, prices and even cease to exist.

• Can become expensive in the long term. 

The use of storage, services and applications that are accessed via the internet rather than being accessed locally on a device.

File storage, e.g. Google Drive

Applications, e.g. Google Docs

• An internet connection is required to access the data.
• Not much control over the security of the data or where it is stored.
• Terms and conditions can be changed with little notice.
• Can be more expensive in the long term.

• Low power, so can operate with a small power source (mobile phone)

• Small in size, so can fit into portable devices (fitness watch)

• Rugged, so can operate in harsh environments (car engine management)

• Low cost, so suitable for mass production (microwave ovens)

ROM is non-volatile, so will store the data and instructions needed to operate the device.

RAM is volatile, so will store the inputs/outputs for the user.

User selection for time, power level,...

Display user selections, timer countdown, ping,...

Many options, discuss: power, size, rugged, cost