[fpc-devel] On a port of Free Pascal to the IBM 370

Mark Morgan Lloyd markMLl.fpc-devel at telemetry.co.uk
Wed Jan 18 13:14:55 CET 2012

Tomas Hajny wrote:

> is nothing like translation between ASCII and EBCDIC because there are
> multiple different character sets for both and real conversion isn't
> possible without taking this into account and knowing the real character
> sets which again depends on the context which is again not known at this
> low level). Unless I'm mistaken, this implies that you indeed need to
> consider the (basic) EBCDIC layout as an alternative to the (basic) ASCII

If the RTL were fully Unicode-aware then possibly this could be handled 
by host localisation, presumably on a classic IBM OS the JCL will state 
unambiguously which variant of EBCDIC is expected.

I think we need to wait for some input from Paul on this one, after all 
he's the project's instigator.

> Not even mentioning the additional "minor" issue with certain characters
> (critical for Pascal source codes) not necessarily directly available in
> _some_ (!) EBCDIC character sets as pointed out by Mark - again something
> which cannot be handled in the general I/O routines because it only
> becomes important when interpreting a general text as Pascal source code
> (in this case, special support on the compiler side will be probably
> necessary, i.e. this should have no impact to RTL, but it will again have
> impact to the common parts of the compiler, namely scanner, not to target
> specific units).

I can't remember the source, but my understanding is that Wirth 
originally worked with an IBM 029 keypunch, possibly connected preparing 
decks for a CDC. He specifically defined (* and *) as digraphs for { and 
}, and I think there were others including (. and .) for [ and ] Did FPC 
/ever/ fully-support these?

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

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

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