Since the Calculator is written entirely in Emacs Lisp, which is not designed for heavy numerical work, many operations are quite slow. The Calculator normally displays the message `Working...' in the echo area during any command that may be slow. In addition, iterative operations such as square roots and trigonometric functions display the intermediate result at each step. Both of these types of messages can be disabled if you find them distracting.
Type m w (calc-working) with a numeric prefix of 0 to
disable all "working" messages. Use a numeric prefix of 1 to enable
only the plain `Working...' message. Use a numeric prefix of 2 to
see intermediate results as well. With no numeric prefix this displays
the current mode.
While it may seem that the "working" messages will slow Calc down considerably, experiments have shown that their impact is actually quite small. But if your terminal is slow you may find that it helps to turn the messages off.