System Control Blocks

Offset
124 (7C) 4
128 (80) 4
132 (84) 4
136 (8S) 4
140 (8C) 4
144 (90) 4
148 (94) 4
152 (98) 4
156 (9C) 4
160 (AO) 4
164 (A4) 4
168 (AS) 4
172 (AC) 4
176 (00) 4
IS0 (B4) 2
Bytes and Field
Alignment Name
CVTIXAVL
CVTNUCB
CVTFBOSV
CVTODS
CVTILCH
CVTIERLC
CVTMSER
CVTOPTOl
CVTTRMTB
CVTHEAD
CVTMZOO
CVTIEFOO
CVTQOCR
CVTQMWR
CVTSNCTR
28 OS System Control Blocks (Release 21.7)
COMMUNICATION VECTOR TABLE
Hex.
Dig. Field Description, Contents, Meaning
Address of the I/O supervisor's freelist pointer
(which contains the address of the next request
element) •
Lowest address not in the nucleus. If the protection
option is specified in the system generation process,
this is a 2K boundary.
If the protection option is not specified in the
system generation process, this is a double-word
boundary.
Address of program fetch routine.
Address of entry point of the dispatcher.
Address of the logical channel word table.
Address of the asynchronous exit queue.
Address of data area within master scheduler resident
data area.
Note: This field should.be used to address the data
area, but not the master common area, of the master
scheduler resident data area. See the note under
CVTMSLT, at offset 60 dec., 3C hex.
Address of branch entry point of post routine.
Address of terminal table present in systems that
have QTAM routines.
Address of the highest priority TCB in the ready
queue.
Highest storage address for this machine (machine
size).
Address of routine which creates IRBs for exits.
Graphics interface task (GFX) field.
If GFX is active:
Address of seventh word of GFX parameter list.
If GFX is not active:
Zero. (Four bytes of binary zeroes.)
Address of system output communications data area
(COA) used by the queue manager, which is stored on
an external device.
Serial number counter.
Counter for assigning serial numbers to non-specific,
unlabeled magnetic tape volumes.
(A binary number forming the XXX part of the volume
serial number of the form LXXXYY.)