Tidal Predictions on a Medium Sized Digital Computer

The University of Cape Town recently acquired an I.C.T. 1301 Computer, and the author undertook to write a Tidal Prediction Programme for the use of the Hydrographic Office of the South African Navy. The 1301 is not a very large or fast machine, and has an Immediate Access Store with storage locations for only 200 main variables, so that is would be unrealistic to expect it to turn out results at anything like the speed achieved by the Liverpool Tidal Institute, using an IBM 7094 or a KDF 9. A further incentive for writing our own programme was that the 1301 has to be programmed in Manchester Auto-Code, and as far as we have been able to ascertain, tidal prediction programmes in this code have up to now not been available, although programmes have been written in the better-known Fortran and Algol source languages. Only a general description of the programme is given here, as anyone wishing to use it may obtain it on punched cards by applying direct to the author. The programme in its present form can utilize up to fifty constituents, and could be modified to handle more. It turns out complete predictions for a port in approximately 75 minutes, as opposed to the roughly ten days needed on the analogue machine previously used. This includes manual operation of the predictor, plus typing of results and proof reading