TclMP is a package that adds multi precision mathematics to Tcl. It is based on the GMP (GNU Multi Precision) library.
Multiprecision numbers are used whenever the numbers don't fit into normal integer or floating point data types. The usual processor provides 32 bit or 64 bit integers and up to 80 bit floating point numbers. If larger numbers or more precision is needed things start to become complicated. Multiprecision maths libraries solve this problem by providing the necessary data types and functions.