The DataFlex Application Development system and accompanying database was, and indeed remains, a highly competent and easy to use toolkit for developing character mode business applications that in some cases became extensive and highly complex,with hundreds of active users.
DataFlex found particularly extensive usage in Government, NHS and Local government organisations, where the relatively simple syntax of the language, its power as a full 4GL and its automatic and bullet proof multi-user capabilities were a perfect match to the burgeoning availability in the mid-1980s of economical and effective multi user Micro computers based around Concurrent CP/M, Turbodos, multiple flavours of Unix and even the DEC VAX range of mini-computer hardware. Plus, as PC networks evolved, DataFlex became available on these, notably Novell, but also Microsoft and some other proprietary network solutions before all coalesced on the early MSDOS networking standard provided in MSDOS v3.1 (for an interesting history of MSDOS and the skullduggery that went on in the early days of PC OS evolution, see this Wikipedia paper).
As a result, some very large systems were built, with hundreds of concurrent users. At one time, you could not lock up a prisoner in a UK jail, park an aircraft at Heathrow, or roster British Rail staff without bumping into a DataFlex presence. And yet, thousands of people (around the world) who had no programming background accountants in particular, but also engineers and in our particular experience, Hospital Facility Management staff, found DataFlex an easy to use system for the creation of solutions to their own, usually business computing, needs. In some cases the tail wagged the dog to the extent that this lead to the creation of new business software development houses.
Many of these systems continue to be used, some 25 years later, with the V2.3 release that was the definitive DataFlex of the 80s surviving into Windows era albeit of course with its green screen Character mode user interface. There can be very few other systems dating from those days of which this can be said.
Object Oriented Programming OOP
Starting with DataFlex 3.0 in 1989, Data Access Worldwide, the authors, took the bold step of introducing Object Oriented programming features to the language. These were largely resisted by the user community, but with the arrival of the first 32Bit Windows version Visual DataFlex, running on Windows 95, this decision was vindicated as all Windows development today is to a greater or lesser extent based on Object Oriented concepts. However it remains the case that Visual DataFlex goes much farther than most in providing a truly OO based development methodology, and its central Data Dictionary based development of the application business rules puts OO to work in truly advanced, but very programmer friendly development framework.
These OO capabilities, and the Data Dictionary controlled development are implemented in the character mode product, the final release of which DataFlex Version 3.2 - also provides compatibility with current Windows operating systems, and with server databases, while still being capable of running 1987 style VDF 2.3 code virtually un-modified.