AQA Computer Science GCSE
Computer Systems - Secondary Storage
Secondary storage is any non-volatile memory which can't ba 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 is the computer's working memory - the RAM.
Three types of secondary storage
There are three categories of secondary storage: magnetic, optical 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 each of the three 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
Optical storage - exam prep
Solid state storage - exam prep
The bullet points on those slides are taken from markschemes for optical and magnetic storage. As of 2021, the exam board has never asked the "explain how it operates" question for solid state storage, so I've come up with a list of points I think would be included for that.
You might find this YouTube video helpful as a summary if you prefer to listen to things. It doesn't quite have the detail about how each type works for top-end marks, but it's a decent job.
There's a lot more detail on solid state storage below. The reasons for this are:
a) it's a bit more complex than the other types
b) it's not come up on a live exam paper yet
c) the exam board seem to like asking 4 mark questions asking you to explain how types of storage actually work. These require some detailed knowledge and they've asked about magnetic and optical storage already.
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.
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.