That Blue Square Thing - AQA GCSE Computer Science

AQA Computer Science GCSE

4.7 Computer Systems – Secondary Storage

There are some changes to this part of the syllabus for the 2027 exam onward. Optical storage (CD, DVD etc...) has been removed, meaning you only need to learn about magnetic and solid state storage. I've removed optical storage from my resources, although the term may still crop up in odd places

Secondary storage is any non-volatile storage mechanism which can't be accessed directly by the CPU.

It includes the hard drive as well as removable media such as USB memory sticks, CDs, DVDs, floppy disks, tape backups and the like.

Secondary Storage Intro – slides from class

Main Memory and Secondary Storage:
Main memory is the computer's working memory – the RAM.

The differences between memory and storage

Data is stored long-term in secondary storage. These are non-volatile storage media which can be changed, deleted and reused. They can even be removed from a computer and used in another one.

Data is copied from secondary storage into main memory when it's needed. It's then worked on and a new version can (but doesn't have to be) saved back on to the secondary storage so that it can be stored long-term.

Two types of secondary storage

There are three categories of secondary storage: magnetic and solid state. Each stores data differently.

Secondary Storage Table – slides from class

Secondary Storage – detailed notes

Based on points from markschemes, I've produced a revision summary for both of the types of secondary storage. This stuff comes up very regularly, so it's well worth taking the time to take a read through these:

Magnetic storage – exam prep

Solid state storage – exam prep

The bullet points on those resources are adapted from markschemes, so they're what the exam board wants to see.

Solid state storage

There's a lot more detail on solid state storage below, just because it's a bit more complex than magnetic storage.

Solid State Storage – detailed notes on slides

The other likely question might be to compare the pros and cons of different storage types. There is a summary of solid state pros and cons on the slides above and detail about the others in the notes above that.

Secondary storage mechanisms can become obsolete. This is worth reading a little about:

How Secondary Storage becomes obsolete

Cloud Storage

Cloud storage involves saving data "in the cloud" and accessing it using the internet – usually using a web browser. This has a number of pros and cons associated with it.

Cloud Storage Intro – slides from class

The detail on cloud storage can be found in the Unit 8 – Cloud Storage page. This part of the syllabus crosses over totally between the two units.