DADiSP - The Ultimate Engineering Spreadsheet

combines the power of sophisticated data analysis with the ease-of-use of a spreadsheet
has a built-in library of over 1,000 scientific and engineering functions
supports up to 100 analysis windows
is designed like a spreadsheet, all data in a worksheet update automatically whenever changes are made
DADiSP's built-in Series Processing Language (SPL) supports user defined functions and custom interfaces using a familiar C/C++ syntax