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Merged
shidel merged 3 commits into from
Jun 20, 2026
Merged

ecm 2026-06a #117

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a0cc6ed
change 21.5F07/.5F08 to DOS 4+, note on mistake
ecm-pushbx Jun 19, 2026
1a739b5
rename 21.5F07/.5F08 files to indicate DOS 4
ecm-pushbx Jun 19, 2026
359b062
describe 21.5F07/.5F08 conditions in detail
ecm-pushbx Jun 19, 2026
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10 changes: 9 additions & 1 deletion ...n Calls/INT 215F07 DOS 5 ENABLE DRIVE.txt → ...n Calls/INT 215F07 DOS 4 ENABLE DRIVE.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -5,14 +5,22 @@
Flag: n/a
----------------------------------------------------------------------------

INT 21 - DOS 5+ - ENABLE DRIVE
INT 21 - DOS 4+ - ENABLE DRIVE
AX = 5F07h
DL = drive number (0=A:)
Return: CF clear if successful
CF set on error
AX = error code (0Fh) (see #01680 at AH=59h/BX=0000h)
Notes: simply sets the "valid" bit in the drive's CDS
in MS-DOS v4.01 and v5.00, the drive is checked to exist in the
CDS array and it is checked that the DPB pointer's low word
is not zero, see offset 45h in #01643. if these conditions
are met, the offset 43h flag mask 4000h ("physical drive") is
set, otherwise error 000Fh is returned.
this function is not supported by Novell DOS 7 through at least
Update 4, but support was added by Update 13
previous revisions of this entry claimed it was a "DOS 5+"
function, however the 2024 April release of MS-DOS v4.00
source texts under the MIT license show it already existed
SeeAlso: AH=52h,AX=5F08h"DOS"

10 changes: 9 additions & 1 deletion ... Calls/INT 215F08 DOS 5 DISABLE DRIVE.txt → ... Calls/INT 215F08 DOS 4 DISABLE DRIVE.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -5,14 +5,22 @@
Flag: n/a
----------------------------------------------------------------------------

INT 21 - DOS 5+ - DISABLE DRIVE
INT 21 - DOS 4+ - DISABLE DRIVE
AX = 5F08h
DL = drive number (0=A:)
Return: CF clear if successful
CF set on error
AX = error code (0Fh) (see #01680 at AH=59h/BX=0000h)
Notes: simply clears the "valid" bit in the drive's CDS
in MS-DOS v4.01 and v5.00, the drive is checked to exist in the
CDS array and it is checked that the DPB pointer's low word
is not zero, see offset 45h in #01643. if these conditions
are met, the offset 43h flag mask 4000h ("physical drive") is
cleared, otherwise error 000Fh is returned.
this function is not supported by Novell DOS 7 through at least
Update 4, but support was added by Update 13
previous revisions of this entry claimed it was a "DOS 5+"
function, however the 2024 April release of MS-DOS v4.00
source texts under the MIT license show it already existed
SeeAlso: AH=52h,AX=5F07h"DOS"