Foreword re C. S. Wallace

One of the second generation of computer scientists, Chris Wallace completed his tertiary education in 1959 with a Ph.D. in nuclear physics, on cosmic ray showers, under Dr Paul George at Sydney University. Needless to say, computer science was not, at that stage, an established academic discipline. With Max Brennan and John Malos he had designed and built a large automatic data logging system for recording cosmic ray air shower events and with Max Brennan also developed a complex computer programme for Bayesian analysis of cosmic ray events on the recently installed SILLIAC computer. Appointed lecturer in Physics at Sydney in 1960 he was sent almost immediately to the University of Illinois to copy the design of ILLIAC II, a duplicate of which was to be built at Sydney. ILLIAC II was not in fact completed at that stage and, after an initial less than warm welcome by a department who seemed unsure exactly what this Australian was doing in their midst, his talents were recognized and he was invited to join their staff (under very generous conditions) to assist in ILLIAC II design. He remained there for two years helping in particular to design the input output channels and aspects of the advanced control unit (first stage pipeline). In the event, Sydney decided it would be too expensive to build a copy of ILLIAC II, although a successful copy (the Golem) was built in Israel using circuit designs developed by Wallace and Ken Smith. In spite of the considerable financial and academic inducements to remain in America, Wallace returned to Australia after three months spent in England familiarizing himself with the KDF9 computer being purchased by Sydney University to replace SILLIAC. Returning to the School of Physics he joined the Basser Computing Laboratory under Professor J.M. Bennett. Between the years 1964 to 1968, among other tasks, he wrote utility software for the KDF9 computer and, with Brian Rowswell, redesigned and rebuilt the Direct Memory Access subsection of the KDF9, increasing its peak channel performance while halving the hardware. Also with Brian Rowswell he designed and constructed a high speed data link between the KDF9 and a Control Data Computer. It was during this period that he published a suggested design for a fast multiplier/divide unit, now known as the Wallace Tree [256, 254]. This design eventually formed the basis of multiply units in most modern computers. Other achievements during this fruitful period included the development of the hardware component of the undergraduate course in computing and, in 1967, of the first Honours level Computing Course in Australia. He also developed a program for the analysis of urban water reticulation networks using automatic block relaxation which was widely used by New South Wales water authorities. In 1968, with David Boulton, Wallace developed the ‘SNOB’ program for unsupervised classification which was the first application of Minimal Message Length (MML) inference [290]. That same year he was appointed Foundation Professor (Chair) of the Department of Computer Science (initially called Information Science) at Monash University. The following years were not easy. Computer Science in the early years was (and some would say still is) widely either misunderstood or an altogether unknown quantity in Science as well as the Humanities. The struggle to establish it as an academic discipline rather than simply a ‘trade skill’ consumed much of his energy for many years in this post, and depleted his health. Nevertheless, he found the time and energy actively to supervise PhD students in subjects as