Most computer users are familiar with the problems of sharing software with others, and the transfer of programs from one computing environment to another. Software represents an ever-increasing proportion of the cost of computing and these costs tend to nullify all the economic advantages flowing from the wider availability of cheap hardware. Years ago it was hoped that the widespread use of high-level programming languages would help in alleviating the problems of software production, by increasing productivity and by making it simpler for users with similar problems to be able to use the same programs, possibly on different types of machines. It is a common experience that in practice this simple optimism has proved to be unfounded. It was these considerations which led us in 1979 to organize a two-week course on "Programming for Software Sharing" at the European Community Joint Research Centre, Ispra Establishment (Italy), forming part of the regular series of "Ispra Courses". With prominent invited lecturers, local contributions and through discussion sessions we examined with an audience from many countries the problems involved in the sharing and transfer of software, as well as suggesting ways of overcoming them. In our local environment we are faced daily with three problems both from engagements in software exchange in the scientific-technical field on a Europe-wide or world-wide basis, and from work with programming techniques and contributions to the international standardization process.

Software Development Methodology.- The Software Life Cycle.- Design of Programs.- Program Structure.- Programming Languages and Style.- Program Validation.- A Programming Example.- Managing Software Development.- Flexibility.- Flexibility.- Operating System Interfaces.- Language Standards.- Software Tools for Software Sharing.- Program Documentation.- Transfer and Sharing.- Software Transfer and Sharing - An Overview.- The Legal Protection of Computer Software.- Experience in Multi-Machine Software Development: the NAG Library - A Case Study.- Transportable User Documentation for Numerical Software.- Data Sharing in Distributed Computing Systems.- FORTRAN IV Dialect Conversion - A Case Study: CDC to IBM.- Users' Experience: Introduction.- Experience with the RELAP Code.- Experience with the SIMMER II Code.