In April/May 2012, STEP Class Library was renamed to STEPcode. This was done because the old name wasn't accurate - the class libraries are only a fraction of the software.
The STEP Class Library (SCL) originated at the National Institute of Standards and Technology, or NIST. NIST started working with STEP in the 80's and continued until the late 90's. Some components of SCL were originally written in Lisp and then re-written in mixed C and C++ in the early 90's. The rest of SCL was written in C++ to begin with.