A ``real'' software environment for parallel machines must offer many other services besides the parallel language to meet expectations of users of conventional (super)computers. Operating services for SIMD machines are provided by the UNIX host and MIMD machines have also used this mechanism up to now. Intel's new Paragon i860-based machine will feature Mach on each processor. Mach is a sophisticated version of UNIX optimized for distributed computing. Mach currently needs to be augmented by fast dedicated message passing to properly support parallel applications. This highlights the distinctions between ``parallel'' and ``distributed'' computing. A distributed network of, say, workstations is indeed a MIMD distributed memory parallel processor. However, this hardware and its current support software, such as Mach, has lower communication bandwidth and, in particular, higher start-up costs (communication latency) than dedicated parallel machines with their high-performance interprocessor connection network.