Date: Thu, 26 Oct 1995 13:56:10 +0200 (IST)
From: Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>
To: "A.Appleyard" <A DOT APPLEYARD AT fs2 DOT mt DOT umist DOT ac DOT uk>
Cc: DJGPP AT SUN DOT SOE DOT CLARKSON DOT EDU
Subject: Re: Windows 95 long filenames


On Thu, 26 Oct 1995, A.Appleyard wrote:

> The book `Undocumented DOS' (by Andrew Schulman et al, publ. Addison-Wesley)
> says that various DOS interrupts `AH=0x71, AL=0xXX, int21' do the same as the
> corresponding `AH=0xXX, int21' but with Windows95 long filenames instead of
> xxxxxx.xxx DOS filenames. How can a program running under any version of DOS
> find if the (computer that it is on) has these `AH=0x71, int21' interrupts?

Use Int21h/AX=7147h (get current directory).  If it returns with carry 
set and 7100h in AX, then long filenames aren't supported.  This is what 
the _use_lfn() function in v2.0 does.