What is Flash Memory?
Flash memory (NAND/NOR), told as a story about a parts warehouse that remembers its contents even when the garage's power goes off.
Parts must still be there even after closing.Some parts must not vanish when the power is off.
Parts on the workbench vanish once the shop closes.So a separate warehouse that survives power-off is needed.
Flash memory is a warehouse that remembers parts even off power.Flash memory comes in two styles: NAND reads in bundles, NOR reads one slot directly.
NAND yields whole bundles (pages); NOR yields single drawers (bytes).NAND and NOR name the memory cell itself, not the FTL software that manages it.
NAND is for bulk storage; NOR is for small code storage.Separate software inside an SSD — the FTL — manages the NAND warehouse.
Flash memory is a warehouse that remembers its contents even off power — in two styles: NAND, which reads and writes whole pages and erases whole blocks, and NOR, which yields single bytes directly.
Flash memory is non-volatile semiconductor storage that keeps data without power. NAND reads and writes by the page and erases by the block; it's cheap and high-capacity — used in SSDs, USB drives, and memory cards. NOR allows byte-level random reads and execute-in-place (XIP), making it common for small firmware storage, though it also erases by the block. The software layer that maps addresses and manages wear on NAND chips inside an SSD is the FTL.
When grown-ups say it
- NAND Flash
- A big warehouse that yields whole bundles (pages) and erases whole boxes (blocks). Cheap and roomy — used in SSDs.
- NOR Flash
- A drawer cabinet that yields a single byte at a time. Costlier, but allows execute-in-place.
- Non-Volatile Memory
- Storage that keeps its contents when power is off. Flash is a prime example.
- Block/Page
- The warehouse's boxes and the slots inside them. NAND erases by the block and writes by the page.
- Erase-before-Write
- The box must be emptied before new parts go in. A constraint across flash; NOR has it too.
- Execute-in-Place
- Running code straight from the drawer (NOR). A NOR advantage — NAND can't do this.
- SSD
- A storage drive built from NAND warehouses. Inside, the FTL manages its blocks.
- FTL (Flash Translation Layer)
- The software that remaps which boxes are used inside the warehouse. Not the cell type itself, but the software managing it. → the parts-warehouse manager who never overwrites