When digital computers first became available many of us expected that they would have an early and significant impact on engineering design. This did not happen, and the reasons why it did not are worth examining. For one thing, the early computers were not nearly large enough; engineers do not build things out of spheres and parallelograms as mathematicians do, and quite a lot of storage space is needed to describe a typical problem in engineering design. Unfortunately, the big computers when they came were so expensive that it was not considered economic to allow users to handle them personally, and batch-processing techniques were introduced. The result was to create a barrier between the computer and the design engineer, and to make it impossible for him to get results of any kind without a delay amounting to a few hours at the very best, and often to much more. Emphasis in fact, was put on the efficiency with which the central processor of the computer was used and no regard at all was paid to the efficiency with which the users—in this case programmers and design engineers—worked. We are on the threshold of a development which, there is every reason to hope, will change the situation radically.