And

is a dyadic scalar boolean function which tests if both arguments are true: it returns 1 if both are 1 and 0 if one or both are 0. It represents the logical conjunction in Boolean logic.

Examples
The following shows all possible combinations of inputs as a Boolean function.

When combined with Reduce, And can be used to test if every value in a Boolean vector is true.

Extended definition
Many APL implementations extend this function to non-Boolean arguments. In this case, this function behaves as Least Common Multiple or LCM. For positive integer arguments, it is defined as the smallest positive number which is divisible by both numbers. If one of the arguments is zero, the LCM function returns zero.

While the mathematical definition of LCM does not cover non-integers, some implementations accept them as arguments. In this case, the return value of  is chosen so that both   and   are integers (or Gaussian integers, when X and/or Y are complex numbers).

Documentation

 * Dyalog
 * APLX
 * J Dictionary, NuVoc