Computing comprises three distinct strands: hardware, software and the ways they are used in real or imagined worlds. Its use in research is more than writing or running code. Having something significant to compute and deploying judgement in what is attempted and achieved are especially challenging. In science or engineering, one must define a central problem in computable form, run such software as is appropriate and, last but by no means least, convince others that the results are both valid and useful. These several strands are highly interdependent. A major scientific development can transform disparate aspects of information and computer technologies. Computers affect the way we do science, as well as changing our personal worlds. Access to information is being transformed, with consequences beyond research or even science. Creativity in research is usually considered uniquely human, with inspiration a central factor. Scientific and technological needs are major forces in innovation, and these include hardware and software opportunities. One can try to define the scientific needs for established technologies (atomic energy, the early semiconductor industry), for rapidly developing technologies (advanced materials, microelectronics) and for emerging technologies (nanotechnology, novel information technologies). Did these needs define new computing, or was science diverted into applications of then-available codes? Regarding credibility, why is it that engineers accept computer realizations when designing engineered structures, whereas predictive modelling of materials has yet to achieve industrial confidence outside very special cases? The tensions between computing and traditional science are complex, unpredictable and potentially powerful.