RECORD CONTROL BYTE (RCB; OIIITTTT a 7 To identify each record type within a transmission block OIIITTTT --or--
o 1110000 III
--or--
o
IIITTTT
TTTT 00000000 1 000 001 010 011 100 101 111
1 0001 0010 0011 0100 0101 0110 0111 1000-1100 1101-1111 End of transmission block
Non-EaT RCB III is control information:
Reserved
Request to initiate a function
transmission (prototype RCB for
function in SRCE )
Permission to initiate a function
Transmission (RCB for function
contained in SRCB )
Reserved
Reserved
Available for location modification
General control record (Type
indicated in SRCB) Non-EaT RCB
III is used to identify streams
of multiple identical functions
(such as multiple print streams
to a multiple printer terminal).
TTTT is the record type identifier. Operator message display request Operator command
Normal input record Print record Punch record
Data set record
Terminal message routing request
Reserved
Available to user
352 IBM VM/310 System Programmer's Guide

SUB-RECORD CONTROL BYTE (SRCB) To provide snpplemental information about a record The contents of this control block depend upon the
record type. Several types are shown below • • ,.CHAR •• o 1 To identify the type of generalized control record !!i1§: CHARACTER
OMCCCCCC
o 1
A
B
C
D
E
F
G
H
I-R
s-z
Initial terminal sign-on
Final terminal sign-off
Print initialization record
Punch initialization record
Input initialization record
Data set transmission
initialization
System configuration status
Diagnostic control record
Reserved
Available to user To provide carriage control information for print records
CCCCCC
1
o
1 000000 OOOONN 01NNNN 1000NN 11NNNN Normal carriage control
Reserved
Suppress space
Space nn lines after print
Skip to channel nnnn after print
Space immediate nn spaces
Skip immediate to channel nnnn
Appendix B: MULTI-LEAVING 353