Airborne computing has been with us since the very early days of aviation when it comprised such basic calculations as TAS from the observed parameters of IAS, temperature and altitude. The display requirement for this type of computing was virtually negligible. However it was appreciated that where instruments could take over the repetitive processes of navigation the aviator could devote his time to tasks which he could perform better than the machine, calculations which he could perform more speedily or more economically than the technology of the time made possible and those which required the intuitive reasoning which has always made navigation a combination of art and science. The Air Position Indicator is an example, and its logical extension the Ground Position Indicator. These analogue computers not only freed the navigator from a great deal of repetitive work but provided a consistent accuracy, and some limited tactical flexibility. The demand for display was still small and easily accommodated in the relatively uncluttered crew positions in early aircraft. As aircraft systems became more complex and speeds increased, the increased workload meant that the crew were not capable of accepting all the information from the increasing number of sensor displays and calculating position, heading to fly, E.T.A., fuel state, and so on, with sufficient rapidity for the required accuracy to be maintained. With the aircraft coming into service it was also necessary to consider optimum altitude and minimum-fuel flight paths.