A Technique for Computer Flow Chart Generation

One of the concerns of the Centre for Computing and Automation at Imperial College is the teaching of good programming practice. To this end new courses have been devised, and tested in practice, with the object of giving students a good grasp of programming techniques, and not just a knowledge of, say, FORTRAN coding. Flow charting is taught as an integral part of the overall problem-solving effort required to implement any algorithm on a computer; as an aid to be used throughout the design and development stages of a program, as well as for final documentation. Flow charts are also extensively used as lecturing aids, illustrating the logical facilities of the programming language in a graphic manner, and also demonstrating good program design features. There is some tedium in producing flow charts for our lecture notes, which are distributed, and also in the general production of flow charts in a neat form for final documentation. It was decided, therefore, to investigate the possibility of producing flow charts automatically, and various approaches were examined, notably those described in Sherman (1966), and Roberts (1967). These approaches suffer from the main drawback that it is assumed that the text of the program contains sufficient information to describe the function of the program completely and clearly. We have found that, in general, production programs do not contain enough relevant information to enable a new reader to understand their function. Neither the variable names used, nor the usually sparse comments in the text, bear any close relationship to the function of the program. For instance the FORTRAN variable XT may refer to 'Time' in one section of a program and 'Distance' in another, and we have also found that programmers are reluctant to insert comments into the text in other than a cryptic manner. The flow chart generator that resulted from our study, called ICFLOW,f produces a conventional layout of boxes and arrows for any number of program routines at one time, within machine storage limitations, with no attempt made to insert text into the boxes, for the