Az-Prolog

A Prolog development system from Japanese company Sofnec originally introduced in 1989 for OS/2 and sundry UNIX systems, with a 32-bit extended DOS, DOS/V and Microsoft Windows ports showing up a few years later.

History
The program traces its roots to the operating system that ran on the Mitsubishi "Melcom PSI" and PSI-II computers that were a fifth generation computer system shipped in 1986 that sported a custom designed 40 bit processor, the PSI had a Prolog based operating system and a Prolog compiler that compiled to p-code and was at the time considerably faster at executing Prolog code that available mini & microcomputers and workstations.

Features
Similarly to a PSI, the Az-Prolog system supported an interpreter and a p-code compiler and later gained a compile to C function so that programmers could deliver small native application without the need for a runtime (this function is intended for CGI programs etc., rather than full blown systems). The Az-Prolog gained a considerable popularity in Japan, not the least since it allowed some compatibility with the PSI but could be run on an OS/2 system that cost only a fraction of the price that the PSI commanded.

However the supplied Prolog interpreter was actually slower than the average interpreter running on a fast PC system and while there existed slower Prolog interpreters out there, particularly in the DOS world, they were also considerably cheaper and the p-code compiler. While faster than most interpreter came out at a time when there was a glut of new Prolog compilers and semi-compilers arriving on the market, most of them developed in Japan, and the Az-Prolog one was not particularly fast and thus suffered in comparison. So even though the system was stable and an excellent development system it became more of a local phenomenon in Japan and was never seriously marketed outside of its home country.

It is currently still being developed for Windows, Linux and Mac OS X and it appears that a version for 32 bit OS/2 never materialised.

Links

 * Sofnec Co. homepage
 * Rudimentary release history
 * Melcom PSI info page