Eumel (pronounced oimel) is an operating system built by GMD in 1979. Originally written for the Z80 processor it was later ported to many different architectures. One of the main concepts of Eumel was that it was persistent and had a microkernel architecture. Persistance in this case meant that if the power failed you would only lose a couple of minutes of work, and upon startup you would continue working from the previous fixpoint. This is also known as orthogonal persistance . Eumel was followed by L3 and later BirliX .