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Digital Research
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Sepp J Morris
2020-11-06 18:50:37 +01:00
parent 621ed8ccaf
commit 31738079c4
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CPM OPERATING SYSTEMS/CPM 2.X/CPM 2.2/PATCHES/MANUAL80.ADD Normal file
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UNDOCUMENTED CP/M FUNCTIONS cont.
From Microsystems, May 1983, p.70
CP/M issues a dummy call to the BIOS 'HOME' routine prior to a
directory read.
Early versions of the 'CP/M 2.2 Alteration Guide' did not include
the following sentence in the description of the SELDSK function of
the BIOS:
The least significant bit of register E is zero if
this is the first occurrence of the drive select
since the last cold or warm start.
This information can provide a clue to the BIOS that it may need to
log-in a disk that has been changed.