Introduction: Logic NAND Gate
A NAND gate is also referred to as a NEGATED AND gate. It is the opposite or inverse of a simple AND gate. With the AND gate the output was forced to a logic HIGH (1) only when both inputs where forced to logic HIGH (1), but with a NAND gate the output is forced to logic LOW (0) when both inputs are forced to logic HIGH (1) and the output is forced to logic HIGH (1) in all other situations. The symbol and truth table for an NAND gate can be seen here.