this is a very natty desk calculator. it displays and
calculates to 14 digits. see here sqrt(99).
it functions like most desk calculators, where the plus button is
predominant and = is only used for * and /
there are two memories I and II. when used small annunciators appear on
the left of the display.
the left side of the keyboard offers a generous array of memory
operations. you can add or subtract the current number to memory within an
operation (M+ and M-)
or you can complete the operation and add or subtract the result from
memory (=+ and =-)