NAND or NOT AND Flash Memory is the most common type of memory. It is used in a variety of storage devices, including SSDs, USB flash drives, and SD cards. NAND memory is non-volatile, meaning it can retain stored data even when the power is turned off.

NAND is a non-volatile memory device that stores blocks as opposed to data bytes as in NOR flash. It has been developed to have lower cost, durability and read/write performance than NOR flash. Because NAND flash stores more data in the same physical area of silicon, chip densities increase and manufacturing costs decrease. It is different from volatile memory, such as DRAM, which loses its contents when power is turned off. NAND flash's block architecture, better performance, and durability make it ideal for storing large amounts of data.

This type of memory is called "NOT AND" because it is reasoned with a boolean (true-false) operator. The NAND operator produces a FALSE value only if both values of its two inputs are TRUE. It can be compared with the NOR operator, which produces only one TRUE value if both inputs are FALSE.

NAND Flash Types

Data stored in NAND Flash is represented by electrical charges stored in each NAND cell. The difference between Single Level Cell (SLC - Single Level Cell) and Multi Level Cell (Multi Level Cell) NAND is how many bits each NAND cell can store at a time.

SLC NAND stores only 1 bit of data per cell. 2-bit MLC NAND stores 2 bits of data per cell. 3-bit MLC NAND (TLC - Triple Level Cell) stores 3 bits of data per cell. Quad-Level Cell (QLC - Quadruple Level Cell) stores 4 bits of data per cell.

The fewer bits per cell, the smaller the capacity. But data is written and retrieved faster. The NAND chip will last much longer because it has a higher endurance level.

As a result, SLC is the fastest and has the highest endurance, but at a lower capacity (typically up to 64GB). TLC and QLC have low endurance but a much higher capacity.