The fact command computes n!.

If n is not an integer returns fact(int(n)).

If n is negative, returns 1.

$\mathrm{MapleTA}:-\mathrm{Builtin}:-\mathrm{fact}\left(4\right)$

$24$

The MapleTA[Builtin][fact] command was introduced in Maple 18.

For more information on Maple 18 changes, see Updates in Maple 18.