Eval is an interactive floating point C-like expression
evaluator. You give it an expression with numeric constants
and variables and functions, and it churns out a numeric
answer. You can use it to immediately evaluate an expression
from the DOS prompt, or you can run it interactively, storing
variables as you go so that you can do more involved
calculations. To use Eval, just give it an expression:
or just run Eval without arguments. Documentation is built-in. Eval's features
include good precision, input and output in any number base, a
large number of built-in functions and constants, flexible numeric
output format, and ability to save and recall sessions from disk.
The source code is included with this distribution.
(excerpted from readme.doc)