Clipper 5.3 Programming Language for DOS
Back in the day (in my case around the early 1990's) this is what I developed various application programs in. I was employed by the South African Police and developed LAN based applications such as a petrol system (which helped automate the completion of the month end vehicle petrol usage stats, and which had to be printed in red font on a specific form - which meant learning to precisely control and Brother Laserjet printer and supplying police stations with a red toner cartridge), a Questions and Answers system (called Q&A System which allowed types of questions to be compiled and which accordingly produced statics of the answers per type of question), an One Independent Variable Regression stats program (called OIVR), and many others.
Because we supported users over 550km away we had to design the applications very robustly allowing for control over re-indexing by users, adjustments to the VAT rate, automating backups to multiple floppy discs, etc. Years after I left, I was surprised to hear that the Petrol System was still in use because it could adjust and recover for most scenarios.
Screen layouts, login security (using a Novell library to test for login and membership of a group), were all modular and designed once and used many times. We tried as much as possible to have everything data driven too from separate databases. I remember using Blinker for the compiling and a DBase III editor for editing databases. Upgrades would check the previous version number and apply the database and index changes automatically.
Books that I had studied cover to cover were (Why? Because there was no YouTube, Google or Internet):
* Straley's Programming with Clipper 5.0
* The Clipper Interface Handbook
* Straley's Programming in Clipper
* Schinkel's Programming in Clipper 5
* QUE's Using Clipper
* HP Laserjet Programming
Below is a short screencast of a donations management system I wrote in my private time for a charitable organisation. It followed the same screen layout standard and menus we used at work. This system allowed for a main admin centre which received updated information via floppy discs from decentralised centres. It shows how the VAT rate etc could be adjusted by the users. I've also attached a short piece of source code from the main module. I have the original EXE file and it runs just fine on Linux using DOSBox. After 25 years it happily recreated it indexes and took off like new.