[fpc-devel] FPC and IBM mainframes

[Mark Morgan Lloyd]

Any discussion of this has, unfortunately, gone very quiet. However, 
while it wasn't me who raised it I continue to poke around, and have 
come up with a couple of relevant points.

The first is that somebody suggested using MUSIC/SP as a development 
platform since it has a degree of TCP/IP support (if run on its 
dedicated Sim/390 emulator, which is Win32-only). In practical terms 
this isn't strictly necessary, since standard IBM terminal clients 
(x3270, tn3270) support a file-transfer protocol which is implemented at 
the mainframe end by a program called IND$FILE.

The second, possibly more interesting, is that while the 
freely-available "classic" IBM operating systems allow a program to have 
a 24-bit address space (i.e. an absolute maximum of 16Mb, including 
kernel entry points etc.), they've been "retrofitted" by enthusiasts 
with extensions to increase the address space to 31 bits. This is 
sufficient to allow GCC to run natively, and as such it should be 
possible to get FPC running on the target system rather than messing 
around with the compilation on a PC and the assembly/linkage on a 
mainframe (or, more likely, a mainframe emulated by Hercules).

I've added minimal descriptive text plus a couple of links at 
http://wiki.lazarus.freepascal.org/Qemu_and_other_emulators#IBM_S.2F370.2C_S.2F390.2C_and_the_S.2F380_.22hack.22 
, and will continue to poke around between other work.

-- 
Mark Morgan Lloyd
markMLl .AT. telemetry.co .DOT. uk

[Opinions above are the author's, not those of his employers or colleagues]