06.041 How can a BASIC program tell which DOS it's running under?
Description
This article is from the Apple II Csa2 FAQ, by Jeff Hurlburt with numerous contributions by others.
06.041 How can a BASIC program tell which DOS it's running under?
A pretty good way is to check the three-byte JMP command starting at
$03D0. If it's 4C 00 BE, you're running ProDOS; if it's 4C BF 9D, you're
running DOS 3.3 or a compatible variant (such as Prontodos).
Two (moderately rare) factors may change the DOS 3.3 JMP: 1- On old
"slave disks" created on sub-48k Apple II's, DOS loads in at a lower address;
2- DOS 3.3 is sometimes moved up into the Language Card. So, your best
procedure is probably to check for ProDOS and, if it isn't ProDOS, just presume
that it's DOS 3.3.
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