The PC-User’s Guide to Colossus

Personal computers (PCs) dominate today’s digital landscape. The two-letter name started with the 1981 IBM PC. Desktop machines based on single-chip microprocessors—and thus called microcomputers—were widely used before the IBM PC, but that is the name that has stuck. Many would consider a Packard-Bell tabletop computer of the early 1960s to be the first personal computer. But as far as single-user/operator commercial machines go, there is also the Bendix G15 from the mid-1950s, described in Chapter 9. PC users are likely to have forgotten or never known the atmosphere of early-generation computers. The ‘operating system’ was a schedule for the human staff who mounted large reels of tape, toggled inputs at the long control panel, pushed the load-and-run switch, and stacked punch cards and fanfold sheets of printed output. The numerous operators wore white lab jackets, worked in large air-conditioned spaces, and appeared to be high priests and acolytes in a vocational order. The users were supplicants. Apart from experimental machines at universities—such as MIT’s famed TX-0 (1955–6), which was controlled by the first computer hackers once it moved to the MIT campus in 1958—the users entreated the operators through written requests heading a card deck. Back then, the users as well as the general public stood behind a velvet rope, even a window wall. The operators continued to rule the machine long after users had electronic connection through time-sharing remote terminals. But those who had hacked the small machines like the TX-0 knew that the goal was the direct, immediate access of personal computers. Colossus already had that personal touch. Designed to be used by a single cryptanalyst assisted by one Wren, and later often run by the Wren solo, Colossus was in that sense a personal computer. But just how close was Colossus to being a PC? This chapter compares and contrasts the architecture of Colossus with that of today’s personal computers. An architect designs a building by balancing needs and functions with resources and aesthetics. The availability and cost of components constrain her work. Physical limitations and dynamics of use further impact on it. The building reflects the architect’s imagination and skill.