 Each user had an 11 megabyte virtual machine (with a strange 3 megabyte memory gap in the middle) and, from 1984 onwards, could run several programs at a time.The operating system was sparsely documented but was written first by Charles Brown, a BU doctoral student, and John H. Porter, a physics PHD, who later became the head of the VPS project (and eventually Boston University's vice president for information systems and technology).Marian Moore wrote much of the later VM code necessary to run the VPS system.