I&#x27;m talking more codebase wise, not protocols, languages, specifications and franchises.<p>For example, Wii U mario games aren&#x27;t using code from the original 8bit mario games.  Same with most SMTP servers today.  SMTP is old, the current implementations in use most of the time are not that old.  I think many unix tools in use today like grep are probably not using the original grep implementations either.<p>So I covered most of the list with UNIX (OSes), Oracle (DBs) and mainframes. I did miss compilers, vim &amp; emacs but even that is being replaced by guys like LLVM.