Table 11 RELATIVE FILE FORMAT
DATA BLOCK
Byte Definition
0,1 Track and sector of next data block.
2-255 254 bytes of data. Empty records contain FF (all binary
ones) in the first byte followed by 00 (binary all zeros) to
the end of the record. Partially filled records are padded
with nulls (00).
SIDE SECTOR BLOCK
Byte Definition
0,1 Track and sector of next side sector block.
2 Side sector number. (0-5)
3 Record length.
4,5 Track and sector of first side sector (number 0)
6,7 Track and sector of second side sector (number 1)
8,9 Track and sector of third side sector (number 2)
10,11 Track and sector of fourth side sector (number 3)
12,13 Track and sector of fifth side sector (number 4)
14,15 Track and sector of sixth side sector (number 5)
16-255 Track and sector pointers to 120 data blocks.
I/O CHANNELS
When a channel is opened to a previously existing file, the DOS will position to
the first record provided that the given parameters match properly. The record
length variable is not necessary on the OPEN if the file is already in existence,
but the DOS causes a check to be made against the record size that was origi-
nally made in the DOPEN statement creating the file. If these do not match,
then error 50 -record not present- will be generated.
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