The basic operations (addition, subtraction, multiplication, division, power to an integer) are implemented by TeX macros in this package. Operands may be numbers with arbitrary numbers of digits; scientific notation is allowed. The expression scanner is also provided. As of version 1.4 (December 2015) the calculation of common functions (sqrt, exp, ln, sin, cos, tan, asin, acos, atan, pi) with arbitrary precision in the result has been added. Exhaustive documentation (including detailed TeXnical documentation) is included. The macro includes many optimizations and uses only TeX primitives (from classic TeX) and \newcount macro.