Legacy Software  

"Rewrite it and retire – I think not!"  

"We have some maths kernels that have taken 30 years to develop and debug"

"They run on an obsolete computer system - we have been advised that we will have to rewrite them"

These were the words from the oil company manager.

"Well if they took you 30 years to write and debug and you want to rewrite them, that’s going to be expensive"

We said, "let's take a closer look".

In reality the oil company possessed some very complex computer models written in Cobol and Fortran. These languages were popular on older mainframe systems. Fortran was and still is a good mathematical/modelling language. Its name comes from "Formula Translation", which pretty well describes what it is good at.

What the company wanted was the capability for engineers to run these analysis programs on their desktop PCs and on notebook PCs rather than the mainframe computers that were going to be scrapped. After much discussion with Microsoft; this hadn’t been tried on a large scale before; we moved the code from the mainframe to a PC platform.

We then tried building the software on the PC platform. Although the basic language is not platform dependent, often display, input and other peripheral facilities are platform specific. Over a period of a few weeks we made subtle changes to the core code and it built on a PC platform. Once this was achieved we built Windows code libraries called DLLs (Dynamic Link Libraries) that could be run in the MS Windows environment. Once this had been done it was simply a matter of developing modern looking, user friendly interfaces, using modern development systems, such as Visual C++ and Visual Basic.

We moved several million lines of software from the obsolete mainframe to PC platforms in a matter of months. Interestingly, this technique combined with internet technologies allows companies to completely reuse and in fact increase the usage of systems that had previously been thought of as obsolete.