Complex sentence: Turing Plus was explicitly designed to replace the Concurrent Euclid programming language in systems-programming applications, and the Tunis operating system, originally written in ConEuc, was recoded to Turing Plus in its MiniTunis implementation.
Split into simpler sentences: Turing Plus was explicitly designed to replace Concurrent Euclid in systems-programming applications. The TUNIS operating system, originally written in Concurrent Euclid, was recoded to Turing Plus in its MiniTunis implementation.