Ada Kalinda
- Ada Kalinda OS
Brief history and initial objectives
This project dates back from the early 1990ies. A few years earlier computer science had seen two marked evolutions : the Macintosh and the Ada language. Both were, each in its own domain, new worlds. Strangely, those two worlds were quickly disappearing in their initial form. The purity of black and white Macintosh was rapidly superseded by more powerful various machines, color screens, new os versions. Ada 83 stayed confined to some specialized area of high reliability software and twelve years later was "augmented" with Ada 95. This brought rare useful additions and a bunch of new possibilities which were more prone to degenerate the initial idea and the occasion of an added compiler complexity.
Being a Pascalist with a strong allergy to C, Ada 83 was a real wonder and a compiler performance at the time. The inside Macintosh four volumes documentation were a thorough description of the Mac Plus system. I decided to see if rewriting a Mac Plus OS with Ada 83 was possible and brought some clarity and ease of software maintenance. But at the time, Ada cross compiler were rare and costly, so that a rewriting of the OS began in fact in CodeWarrior Pascal. Several machines were used, as the dual PPC/i86 power pc, but development mainly progressed on a Mac LCIII with MetroNub to target an x86 pc. The project advanced up to a functional graphical interface and a start of usable file system. But the Pascal code was becoming very heavy to maintain and an interruption of the development showed that reinsertion in the project was rather difficult and the Pascal code not so easy to comprehend or read.
Time passing, CodeWarrior tools and machines changing, cross development became more difficult and tentative of rewriting in C was done which was quickly abandoned being an horror story in maintenance and reinsertion in source code. Then Gnat appeared and I saw that version 3.15 built on gcc 2.81 could be used with its pragma "No_Run_Time" as a sort of "half cross-compiler" x86 Linux hosted and generating x86 binary executable on a bare x86 pc. A few trials were positive but development was not using a gdb stub and disquettes transfer for execution tests were cumbersome. The boot code was written in this configuration with much pain and beeps and all sort of debugging tricks, those who tried know. Later I decided to use the Bochs emulator to test the binary.
The Gnat 3.15 being an Ada 95 compiler, I took the old Code Warrior Pascal source an decided to rewrite with new objects programming possibilities. It proved that the new Ada was much more prone to spaghetti code than the Ada 83 and that the best option was to adhere as much as possible to Ada 83 programming which imposed more constraints but resulted in better structured and simpler code.
Finally, after many years of instructive trials, I converted the initial Pascal code in something as close as possible to Ada 83, with only the regrettable forced use of child packages. I would have been very glad to be an Ada 83 purist, but child packages really simplify the Macintosh like OS structure of Kalinda.
Only later