*COMDECK  IOTBLD
 IOTBLD   CTEXT  IOTBLD - RANDOM I/O TABLE FORMAT DEFINITIONS 
  
**        RI. - RANDOM INDEX WORD 
  
          DESCRIBE RI.,60    RIW(FLAGS,LEN,[FWA],[LCM],[OFS,RA])
 IC       DEFINE 1           =1  IN CORE, =0 ON MS
 AT       DEFINE 1           ADDRESS TYPE, =0 DISK, =1 LCM
          DEFINE 1
 LEN      DEFINE 18          BLOCK LENGTH (INCORE COPY) 
 OFS      DEFINE 9           BLOCK OFFSET IN RECORD 
 RA       DEFINE 30          DISK ADDRESS OF BLOCK
  
          DESCRIBE RI.,36 
 FWA      DEFINE 18          FWA OF BLOCK IN *BLK*
 LCM      DEFINE 18          LCM ADDRESS OF BLOCK 
 BAW      SPACE  2,8
**        BA. - BLOCK ADDRESS INFORMATION WORD
  
          DESCRIBE BA.,60    BAW(FLAGS,BI,LEN,FWA)
 BLK      DEFINE 1           =1 IF BLOCK IS IN *BLK*
 PRI      DEFINE 1           BLOCK PRIORITY FOR PURGING 
 HB       DEFINE 1           HOLDING BLOCK
 FW       DEFINE 1           FINAL WRITE FLAG 
          DEFINE 2
 BI       DEFINE 18          *BIT* INDEX ( = BN*2 ) 
 LEN      DEFINE 18          BLOCK LENGTH  (INCORE COPY)
 FWA      DEFINE 18          FWA OF BLOCK IN *BLK*
  
 HBB      DEQU   HB,2        HB AND PRI BITS
 SAV      DEQU   BI,23
 SVL      DEQU   LEN,41 
 BHW      SPACE  2,8
**        BH. - BLOCK HEADER INFORMATION WORD 
  
          DESCRIBE BH.,60    BHW(FLAGS,BI,BST,LEN)
 AV       DEFINE 1           =1 BLOCK IS AVAILABLE SPACE
 PRI      DEFINE 1           BLOCK PRIORITY FOR PURGING 
 HB       DEFINE 1           HOLDING BLOCK
 FW       DEFINE 1           FINAL WRITE FLAG 
          DEFINE 2
 BI       DEFINE 18          BIT INDEX, (BN*2)
 BST      DEFINE 18          INDEX TO BST TABLE 
 LEN      DEFINE 18          BLOCK LENGTH 
  
**        BT. - BLOCK TRAILER WORD
  
          DESCRIBE BT.,60    BTW(FLAGS,LKB,LKF,LEN) 
 AV       DEFINE 1           =1 BLOCK IS AVAILABLE SPACE
          DEFINE 5
 LKB      DEFINE 18          ABS LINK BACKWARD
 LKF      DEFINE 18          ABS LINK FORWARD 
 LEN      DEFINE 18          BLOCK LENGTH (INCLUDING EXTRA WORDS) 
  
          ENDX
