System information

The following table lists and describes each of the fields in the File Control Block figure.
Table 5-2. File Control Block Fields
Field Definition
dr drive code (0-16)
0 = use default drive for file
1 = auto disk select drive A,
2 = auto disk select drive B,
...
16 = auto disk select drive P.
f1...f8 contain the filename in ASCII upper-case, with high bit = 0
t1,t2,t3 contain the filetype in ASCII upper-case, with high bit = 0. t1', t2', and t3' denote
the bit of these positions,
t1' = 1 = >Read-Only file,
t2' = 1 = >SYS file, no DIR list
ex contains the current extent number, normally set to 00 by the user, but in range
0-31 during file I/O
s1 reserved for internal system use
s2 reserved for internal system use, set to zero on call to OPEN, MAKE, SEARCH
rc record count for extent ex; takes on values from 0-127
d0...dn filled in by CP/M; reserved for system use
cr current record to read or write in a sequential file operation; normally set to zero
by user
r0,r1,r2 optional random record number in the range 0-65535, with overflow to r2, r0, r1
constitute a 16-bit value with low byte r0, and high byte r1
5.2 Call Conventions CP/M Operating System Manual
5-9