Global Index (all files) (short | long) | Local Index (files in subdir) (short | long)
fac = fact(in);
fac = fact(num); This is the same as num! . e.g., fact(5) = 5*4*3*2*1 etc.
function fac = fact(in); if in == 0; fac = 1; else fac = prod([1:in]); end