Cambridge O Level Computer Science · Syllabus 2210 · Hardware
Solid-State Storage
What is Solid-State Storage?
Solid-state storage is secondary storage with no moving parts, in which data is held by trapping electrons in floating gate transistors using NAND or NOR flash memory, so that the stored charge survives when power is removed.
This definition is part of the Hardware chapter in Cambridge O Level Computer Science.
Solid-State Storage in context
Solid-state storage has no moving parts. It uses NAND or NOR flash technology, in which transistors act as control gates and floating gates. Electrons are moved on to or off a floating gate, which is surrounded by insulating material so the electrons stay where they are put even with the power off — that is what makes it non-volatile. The examples named by the syllabus are the solid-state drive (SSD), the SD card and the USB flash drive.
Common mistakes with Solid-State Storage
- 20. “An SSD has no transistors because it has no moving parts.” Why wrong It confuses “no mechanical movement” with “no components”. Solid-state storage is built almost entirely from transistors. Correct model Solid-state storage uses NAND or NOR flash technology in which transistors act as control gates and floating gates. “No moving parts” means nothing mechanical moves — electrons still do. Exam-safe “Solid-state storage has no moving parts and uses NAND or NOR flash technology, with transistors acting as control gates and floating gates.” Check: what keeps the electrons on the floating gate when the power is off?The insulating layers surrounding it. That is why solid-state storage is non-volatile.
Examiner tips on Solid-State Storage
- Avoid absolute claims. “An SSD never fails” and “optical discs last for ever” are both wrong, and both are easy to write by accident when you are trying to praise a technology. Solid-state storage has a finite number of write cycles per cell and can fail; optical discs scratch, warp and degrade. Write “more resistant to physical shock”, not “indestructible”.
Questions students ask about Solid-State Storage
What is the difference between magnetic, optical and solid-state storage?
Magnetic storage, such as a hard disk drive, uses electromagnets in a read/write head to magnetise regions of a spinning platter in one of two directions, representing 1s and 0s. Optical storage, such as a CD, DVD or Blu-ray, uses a laser to read pits and lands on a disc's surface, which reflect light differently. Solid-state storage, such as an SSD, SD card or USB flash drive, has no moving parts and stores data by trapping electrons on floating gate transistors using NAND or NOR flash technology.