Math Window is a scientific calculator with the look and feel of a text editor. It supports the usual copy and paste hotkeys. (Ctrl-C or Ctrl-Insert for copy and Ctrl-V or Shift-Insert for paste.) It can do addition, subtraction, multiplication, division, square root, exponents, log, trig, inverse trig, modulus, rounding and custom functions tailored to the needs of Electrical Engineers. Math Window understands expressions with an arbitrary degree of nesting and that contains scientific or regular (x.y) notation (or both). Without the overhead of a complete programming environment, Math Window lets you define and use an arbitrary number of semicolon-delimited numerical constants. The program guarantees reliability by employing a Tcl JIT with a quarter century of use behind it. See http://www.cap-tool.com/MathWindow.html for more information.