David Ellison trained as a computer programmer at the University of Manchester. Prior to starting his degree, he worked at Television House in Manchester from February to September 1966. Here he assisted in the running of programs at West Gorton on an FP6000 computer that had been brought from Ferranti Packard in Canada as the prototype for the 1900 series of computers. David learned the programming language Fortran and worked with Peter Stocker, Charles Murgotrough, John Hindley and Dr Printz in the programming team.

David was one of the original undergraduates to follow the University of Manchester's computer science degree course, which was the first course of its kind in the United Kingdom. He studied from October 1966 to June 1968 and was taught by Professor Tom Kilburn, Professor Frank Sumner, Jeff Rohl, Tony Brooker, Derrick Morris and Eric Dunstan. David's final year project was to create a set of graphics primitives that could be output on a Calcomp drum plotter.

David continuted his studies at the University of Manchester on a Masters Degree from July 1968 to Oct 1969. He was supervised by Dr Charles Lindsey and carried out research into the Compiler Compiler work of Tony Brooker.

From 1969 – 1977, David was employed as a systems programmer at the University of Manchester Regional Computer Centre. Together with Richard Collins, David created the in-core Fortran 66 compiler for the 1900 series computers. This program was heavily used throughout the 1970s in many universities. The program enabled students to develop and run programs in a batch environment with the compiler generating code without the need for semi-compiled interim code and with the programs executing with full software protection within the compiler environment.

Much of David's work was done during the development of George 3 and he worked closely with colleagues to help stabilise one of the most user-friendly operating systems that was developed. He worked on the Control Data 7600 and helped develop a symbolic debugging package for their proprietary Fortran compiler.

In 1977, David was appointed as an assistant director to Professor John Larmouth at the University of Salford. Here, he helped run the University’s computing service and assisted in the implementation of the Larmouth scheduler that enabled dynamic scheduling of priority of jobs, based upon individual share allocations and usage.

David went on to head a team that developed a Fortran 77 compiler, initially for the ICL 1900s to replace the earlier version, and subsequently a version was created for the Prime super minis. After this, he became director of the computing service at the University of Salford, and was responsible for the first Novell based computing service for all students using a filestore hierarchical structure and a system of remote booting of the PCs over Ethernet.

In 1997, David took early retirement from the University of Salford, and became a part-time director of Salford Software Limited, a wholly-owned company of the University. The company had been created to capitalise on the University's Fortran 77 compiler for the Prime super minis. The company created Fortran 77, Fortran 90 and Fortran 95 compilers for the Intel 386 processors and upwards, as well as a C compiler and a windows developer tool for Fortran developers. It is still active in these areas as well as supporting the higher education community for Novell networking.