NAME       : HCPRSHBK
 DESCRIPTION: RSPBK Header Block
 DSECT      : RSHBK
 FUNCTION   : Contains RSPBK chain header (there are three
              RSPBK chains) and locks.
 LOCATED BY : SYSPRTT field in SYSCM
              SYSPUNT field in SYSCM
              SYSRDRT field in SYSCM
 CREATED BY : HCPRIO
 DELETED BY : Never deleted

 RSHBK DSECT
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Hex   Dec Type/Val   Lng Label (dup)    Comments
---- ---- --------- ---- -------------- --------
0000    0 Structure      RSHBK          RSPBK Header Block
0000    0 Signed       4 RSHCOUNT       Count of number of RSPBKs
0004    4 Address      4 RSHANCH        Pointer to first RSPBK
       Notes      : There will be three versions of the RSHBK present on
             any system.  One will represent the head of the reader
             RSPBKs, one will represent the head of the printer
             RSPBKs and one will represent the head of the punch
             RSPBKs.  They will be anchored in SYSCM at SYSRDRT,
             SYSPRTT and SYSPUNT, respectively.
             No attempt should be made to acquire the lock
             represented by RSHLOCK while an RDEV lock is held.
             Furthermore, if more than one of these locks needs
             to be acquired, they should be acquired in the order
             of reader, printer and punch and released in the
             oppposite order to prevent possible dead-locks.
             These locks may be acquired by threads that are holding
             an RDEV lock.
0008    8 Dbl-Word     8 RSHLOCK (3)    Lockwords used by HCPLCK to allow
                                        us to manipulate RSPBK chains
0020   32 Signed       4 *              Reserved for future IBM Use
0024   36 Signed       4 *              Reserved for future IBM Use
          00000028       RSHBKLEN       *-RSHBK Length of RSHBK area

          
*** RSHBK - RSPBK Header Block
*
*     +---------------------------+---------------------------+
*   0 |         RSHCOUNT          |         RSHANCH           |
*     +---------------------------+---------------------------+
*   8 |                                                       |
*     =                       RSHLOCK                         =
*     |                                                       |
*     +---------------------------+---------------------------+
*  20 |///////////////////////////|///////////////////////////|
*     +---------------------------+---------------------------+
*  28
*
*** RSHBK - RSPBK Header Block

 
Symbol         Dspl Value
-------------- ---- -----
RSHANCH        0004
RSHBKLEN       0024 00000028
RSHCOUNT       0000
RSHLOCK        0008