More then 12 digit...

[GregLewis]

A while back I worked on a project requiring more than 16 digits of precision. I found that both IBM and Intel have a decimal floating point library that works with 16 and 32 digits. The IBM library is called decNumber and includes a version under the GPL license and a version under the ICU license. I'm not familiar with the ICU license, but their web site says it's simpler and less restrictive. I could not find the license for the Intel code, but the site comes up when searching on "intel decimal floating point math library". Both sets of code are in C and includes the transcendental functions. I believe the Intel code includes additional functions such as gamma. As for a "free" floating point package, there's some projects under LibTomProjects. I believe LibTomMath is an extended integer library, but there's also a LibTomFloat library that is based on the integer code but is an arbitrary floating point library. On the downside, the LibTomFloat library is at version 0.02 and hasn't been updated since 2004. If someone were to build out a floating point library, that's probably a descent place to start given the code is free to use and modify without restrictions.