There a variety of operations that may be performed. For clarification x is the most recently added element, and y is the previous element. The following may not be self-explanitory:
% - Modulous
+/- - Negate - This may be used in entry as well as a stack operation. It may also be used to negate the exponent in exponential notation.
y^x - Raise the y to x.
y^1/x - Find the xth root of y.
x! - x factorial
Ln - find the natural logarithm
log - find the base 10 logarithm
1/x - find the inverse of x.
AND - Bitwise AND
OR - Bitwise OR
Cmp - Ones compliment
Arc/Hyp - These toggle buttons change the meaning of the trigonometric buttons. Hyp will make the Sin button perform the hyperbolic sine. The Arc button will make the Sin button find the Arcsine.