Non-volatile memory (NVM)

Any memory that keeps its contents after the power is switched off — the chip's long-term memory, versus the short-term scratchpad of SRAM and DRAM. Flash is the workhorse NVM, but it's slow to write and wears out, so the industry chases 'emerging' NVMs that aim to be as fast and durable as RAM yet permanent. These store a bit not as charge but as a physical state of the material: the resistance of a tiny filament (ReRAM), the magnetization of a nano-magnet (MRAM), or the crystalline-versus-amorphous phase of a chalcogenide (PCM/phase-change).

The dream is 'storage-class memory' that erases the wall between fast-but-forgetful RAM and slow-but-permanent disk — letting a computer keep working data in place through a power cut. On-chip embedded NVM (eNVM) also stores a microcontroller's firmware, trim values, security keys, and the eFuse settings burned at the factory. Each technology juggles the same trade-offs: speed, density, endurance (how many writes before it dies), and retention (how many years it remembers).