Game Development Reference
switches called logic gates allow for the circuit to be opened or closed,
depending on two incoming electrical currents instead of the one from the
In all, there are seven logic gate configurations that take two currents as input
and output a single current. These gates are called AND, OR, NOT, NAND, NOR,
XOR, and XNOR. The AND gate takes two input currents; if both currents are
on, the output current is on. If only one or none of the input currents is on, the
output is off. This is illustrated in Figure 1.24 .
In computer science, 1 the operation of combining two currents or signals into
one is called Boolean algebra 2 and logic gate names (i.e., AND, OR) are called
Boolean functions , although the on signal in computer science is referred
to as TRUE or the value 1 and off is FALSE or 0. Using this terminology, all
possible functions of the AND gate can be represented in truth tables shown
in Table 1.1 . It should be noted from Table 1.1 that truth tables can be written
in a number of formats using 1s and 0s or TRUEs and FALSEs.
Fig 1.24 A conceptualization of an
AND logic gate.
1 And mathematics, physics, information technology, etc.
2 Named after George Boole, the 19th-century mathematician who first defined algebraic
systems of logic.