PURE, successor to PEACE, is a family of object-oriented, femtokernel operating systems (OSs); it is an acronym for: Portable, Universal Runtime Executive. Goals: strives for very fine granular dynamic reconfiguration, based on passive instead of only active objects; be special purpose OSs with minimal memory use; provide a portable, universal runtime executive for deeply embedded parallel/distributed systems. Deeply embedded systems have extreme resource constraints in memory, CPU, and power use. Most versions have no realtime abilities, but some do (OSEK) and can be used for soft and hard realtime uses.