An attempt is made to show how modular programming techniques could allow a user to build a library of ROMs containing program modules for assembly into alternative applications. Modular programming is now the preferred technique for tackling large software projects. Partitioning a complex application into smaller tasks which may, in turn, be further subdivided, allows large programs to be designed in a systematic manner. Programs designed in this way are more likely to work correctly and will be easier to maintain and document.