Glossary / Semiconductors
NAND
The logical operation that outputs 0 only when both inputs are 1, and 1 otherwise. Combinations of this one operation are enough to build any logic circuit.
In 1913 Henry Sheffer showed that a single operation, meaning that A and B are not both true, suffices to express all of Boolean algebra's AND, OR and NOT[1]. It later came to be called NAND, for NOT AND.
For chip makers this matters a great deal: it guarantees that any computer can be assembled from large numbers of one kind of part. In CMOS a NAND circuit takes four transistors. NAND flash memory, used in USB sticks and solid-state drives, takes its name from the way its memory cells are wired, which resembles this circuit.
Related terms
- Boolean algebraMathematics that represents true and false as 1 and 0 and calculates with AND, OR and NOT much as with addition and multiplication. The foundation of digital circuit design.
- CMOSA circuit style that pairs the two opposite types of MOS transistor. Current flows only at the moment of switching, so power consumption is tiny.
- Flip-flopA circuit that stays in one of two stable states and switches to the other when signalled. The smallest component that can remember one bit.