diff --git a/I1620/i1620_cd.c b/I1620/i1620_cd.c
index 61bfd1a2..2d315d66 100644
--- a/I1620/i1620_cd.c
+++ b/I1620/i1620_cd.c
@@ -73,8 +73,8 @@ UNIT cdr_unit = {
     };
 
 REG cdr_reg[] = {
-    { FLDATA (LAST, ind[IN_LAST], 0) },
-    { DRDATA (POS, cdr_unit.pos, T_ADDR_W), PV_LEFT },
+    { FLDATAD (LAST, ind[IN_LAST], 0, "last card indicator") },
+    { DRDATAD (POS, cdr_unit.pos, T_ADDR_W, "position in the reader input file"), PV_LEFT },
     { NULL }
     };
 
diff --git a/I1620/i1620_dp.c b/I1620/i1620_dp.c
index fcd46b4a..41d60472 100644
--- a/I1620/i1620_dp.c
+++ b/I1620/i1620_dp.c
@@ -120,19 +120,19 @@ UNIT dp_unit[] = {
     };
 
 REG dp_reg[] = {
-    { FLDATA (ADCHK, ind[IN_DACH], 0) },
-    { FLDATA (WLRC, ind[IN_DWLR], 0) },
-    { FLDATA (CYLO, ind[IN_DCYO], 0) },
-    { FLDATA (ERR, ind[IN_DERR], 0) },
-    { FLDATA (DPSTOP, dp_stop, 0) },
-    { URDATA (CYL, dp_unit[0].CYL, 10, 8, 0,
-              DP_NUMDR, PV_LEFT + REG_RO) },
+    { FLDATAD (ADCHK, ind[IN_DACH], 0, "address check (compare error) indicator") },
+    { FLDATAD (WLRC, ind[IN_DWLR], 0, "wrong length record check indicator") },
+    { FLDATAD (CYLO, ind[IN_DCYO], 0, "cylinder overflow check indicator") },
+    { FLDATAD (ERR, ind[IN_DERR], 0, "disk error indicator") },
+    { FLDATAD (DPSTOP, dp_stop, 0, "disk check stop") },
+    { URDATAD (CYL, dp_unit[0].CYL, 10, 8, 0,
+              DP_NUMDR, PV_LEFT + REG_RO, "Cylinder") },
     { NULL }
     };
 
 MTAB dp_mod[] = {
-    { UNIT_WAE, 0, "write address disabled", "ADDROFF", NULL },
-    { UNIT_WAE, UNIT_WAE, "write address enabled", "ADDRON", NULL }, 
+    { UNIT_WAE, 0, "write address disabled", "ADDROFF", NULL, NULL, NULL, "set unit n address enable off" },
+    { UNIT_WAE, UNIT_WAE, "write address enabled", "ADDRON", NULL, NULL, NULL, "set unit n address enable on" }, 
     { 0 }
     };
 
diff --git a/I1620/i1620_lp.c b/I1620/i1620_lp.c
index d0ff98e9..fe33f842 100644
--- a/I1620/i1620_lp.c
+++ b/I1620/i1620_lp.c
@@ -77,17 +77,17 @@ UNIT lpt_unit = {
     };
 
 REG lpt_reg[] = {
-    { BRDATA (LBUF, lpt_buf, 8, 8, LPT_BSIZE + 1) },
-    { DRDATA (BPTR, lpt_bptr, 8) },
-    { HRDATA (PCTL, lpt_savctrl, 8) },
-    { FLDATA (PRCHK, ind[IN_PRCHK], 0) },
-    { FLDATA (PRCH9, ind[IN_PRCH9], 0) },
-    { FLDATA (PRCH12, ind[IN_PRCH12], 0) },
-    { FLDATA (PRBSY, ind[IN_PRBSY], 0) },
-    { DRDATA (POS, lpt_unit.pos, T_ADDR_W), PV_LEFT },
-    { BRDATA (CCT, cct, 8, 32, CCT_LNT) },
-    { DRDATA (CCTP, cct_ptr, 8), PV_LEFT },
-    { DRDATA (CCTL, cct_lnt, 8), REG_RO + PV_LEFT },
+    { BRDATAD (LBUF, lpt_buf, 8, 8, LPT_BSIZE + 1, "line buffer") },
+    { DRDATAD (BPTR, lpt_bptr, 8, "buffer pointer") },
+    { HRDATAD (PCTL, lpt_savctrl, 8, "saved print control directive") },
+    { FLDATAD (PRCHK, ind[IN_PRCHK], 0, "print check indicator") },
+    { FLDATAD (PRCH9, ind[IN_PRCH9], 0, "channel 9 indicator") },
+    { FLDATAD (PRCH12, ind[IN_PRCH12], 0, "channel 12 indicator") },
+    { FLDATAD (PRBSY, ind[IN_PRBSY], 0, "busy indicator") },
+    { DRDATAD (POS, lpt_unit.pos, T_ADDR_W, "position in the output file"), PV_LEFT },
+    { BRDATAD (CCT, cct, 8, 32, CCT_LNT, "carriage control tape array") },
+    { DRDATAD (CCTP, cct_ptr, 8, "carriage control tape pointer"), PV_LEFT },
+    { DRDATAD (CCTL, cct_lnt, 8, "carriage control tape length (read only)"), REG_RO + PV_LEFT },
     { NULL }
     };