This article presents a portable C++ system for multiple precision calculations of special functions callede_float. It has an extendable architecture with a uniform C++ layer which can be used with any suitably prepared MP type. The system implements many high-precision special functions and extends some of these to very large parameter ranges. It supports calculations with 30 ⋯ 300 decimal digits of precision. Interoperabilities with Microsoft’s® CLR, Python, and Mathematica® are supported. The e_float system and its usage are described in detail. Implementation notes, testing results, and performance measurements are provided.