Non-volatile memory (NVM) is a type of memory that retains stored data after the power supply is turned off; only reading or writing data requires power.
Non-volatile memory chips can be utilised by manufacturers for a variety of purposes, including controller code in hard disk drives (HDDs), or in the case of solid-state drives (SSDs), USB flash drives, and SD cards, to store data. NAND flash is the most common type of non-volatile memory used to store data, with several variations including single-level cell (SLC), multi-level cell (MLC), triple-level cell (TLC) and quad-level cell (QLC), which differ based on how many bits are stored in each cell. Manufacturers are constantly developing new non-volatile memory technologies in order to increase storage density, improve performance and endurance, and reduce power consumption. Read-only memory, or ROM, is another type of non-volatile memory, and as the name suggests, it may only be read. ROM is most commonly used for firmware updates.
In contrast volatile memory requires an electric current to retain data; when the power supply is turned off, data is erased. The most common type of volatile memory is RAM, or random-access memory. A computer loads the operating system into RAM when it is powered up, and similarly, applications are loaded into RAM. Because the read/write speed of RAM is incredibly fast, it allows the operating system and applications to run much more smoothly. All data stored in RAM is lost when the host device is powered down, which is why restarting a computer or electronic device is often an effective way to fix any problems. Other types of RAM include system RAM (SRAM), which is generally used as cache memory, and dynamic RAM (DRAM).
