User`s guide

where
dr drive code (O - 16)
0 = > use default drive for file
1 = > auto disk select drive A,
2 = > auto disk select drive B,
16 = > auto disk select drive P.
fl ... f8 contain the filename in ASCII
upper-case, with high bit = 0.
f1'..., f8' denote the high-
order bit of these positions,
and are file attribute bits.
tl,t2,t3 contain the filetype in ASCII
upper-case, with high bit = 0.
tl') t2'1 and t3' denote the
high bit of these positions,
and are file attribute bits.
tl' = 1 = > Read/Only file
t2' = 1 = > System file
t3' = 1 = > File has been archived
ex contains the current extent number,
usually set to 0 by the calling program,
but can range 0 - 31 during file I/O
sl reserved for internal system use
s2 reserved for internal system use
rc record count for extent "ex"
takes on values from 0 - 255
(values greater than 128 imply
record count equals 128)
2-14
2.3 BDOS File System CP/M 3 Programmer's Guide