I could have sworn it was only 1 and 2 that where in plain C with 3 moving towards C++. Maybe not. 4 is certainly C++ though. Either way it is a professional engine and surprising that it was ever open sourced (although part of the GPL release for tech 4 had to be changed due to not having permission to release a particular algorithm I believe). Its not really newbie stuff but its the first thing I could think of.

I could have sworn it was only 1 and 2 that where in plain C with 3 moving towards C++. Maybe not. 4 is certainly C++ though.