A laptop uses a solid state drive (SSD) for secondary storage.
Describe how data is stored on a solid state drive.
Mark scheme
Award up to two marks for a linked description such as:
- Data is stored on (flash) memory chips/cells (1) as a pattern of electrical charges (1)
- A current/voltage forces electrons through a barrier (1) so that they are trapped (or not trapped) to hold/represent a value (1)
- Cells with a trapped charge and cells with no trapped charge (1) represent 1s and 0s/binary (1)
- The trapped charge remains when the power is turned off (1) so the data is not lost/it is non-volatile (1)
Do not accept responses that describe magnetic storage, e.g. magnetised platters, spinning disks or read/write heads, or optical storage, e.g. lasers, pits and lands.
Do not award a mark for 'it is solid state' or 'it has no moving parts' without a description of how the data is stored.
Do not award a mark for restating the stem, e.g. 'a laptop uses an SSD' or 'an SSD uses flash memory'.
'Data is stored as electrical charges' on its own, with no reference to memory chips/cells or to how the charge is held, earns a maximum of one mark (1).
A response that only describes electrons being trapped, with no link to how the value/data is represented, earns one mark (1). The second mark needs a link such as trapped and not trapped charge representing 1s and 0s, or the trapped charge being kept so the data is not lost.
Example answers and how they were marked
A current is used to force electrons through a barrier so that they become trapped, and a cell with a trapped charge or a cell with no trapped charge represents a 1 or a 0.
Why: Linked description: a current forces electrons through a barrier (1) and trapped/not trapped charge represents 1s and 0s (1).
The data is stored in flash memory chips.
Why: Gives the creditworthy point that data is stored on flash memory chips (1) but does not develop it, e.g. by saying the data is held as electrical charges or by describing trapped electrons.
The data is stored as magnetised areas on a spinning platter.
Why: This describes magnetic storage, which the mark scheme says not to accept for a solid state drive.