Control Data 3170 Installation Handbook page 270

9.1.6 At TERING MSOS FILES
The user may alter and add to the MSOS system files, resident, ABS, and LIB, through
the PRELIB routine which is contained in the LIB file (refer to PRELIB, section 8).
9.2 OCAREM FILES
9.2.1 FILE LABEL DIRECTORY (FLO)
The FLD is used to provide access to all files maintained by MSOS and is composed
of two separate files, IDFILE and LABELFILE. An entry is made in each of the FLD
files each time a file is created.
lABElFllE (FO 66)
LABELFILE entries are fixed-length file labels having a block size of 50 + 3 (MSC)
words, where MSC is the maximum allowable segment count (defined by the installation
during IUP processing.
I
The entries for a given file occupy the same relative positions within IDFILE and
LABELFILE. Thus, to locate a specific label one can search IDFILE until the desired
identification is found, then compute the block number within LABEL FILE at which the
label is stored.
The first label in LABEL FILE is for LABELFILE itself. The labels for IDFILE and
MSDFILE occupy blocks 2 and 3, respectively, followed by the labels for the four MSOS
system files.
A mass storage file label is composed of a fixed 50-word base plus three additional
words for each segment of the file. OCAREM is capable of processing files which
contain up to 63 segments although installations may set the maxinlum allowable segment
count to some value less than 63 if they wish. The format of a file label is shown in
Figure III- 9-2 and described in Table III- 9-1.
60410800 D
III-D-5