diff --git a/ReadMe.md b/ReadMe.md
index b5dbdb74..b7cfc40e 100644
--- a/ReadMe.md
+++ b/ReadMe.md
@@ -101,6 +101,27 @@ executable binary.
 
 Execute as usual on Linux ('./hello') or Windows ('hello').
 
+In order to know module's interface, use "showdef" program.
+
+```
+ $ showdef Out.sym
+DEFINITION Out;
+
+  VAR
+    IsConsole-: BOOLEAN;
+
+  PROCEDURE Char(ch: CHAR);
+  PROCEDURE Flush;
+  PROCEDURE Int(x: INT64; n: INT64);
+  PROCEDURE Ln;
+  PROCEDURE LongReal(x: LONGREAL; n: INT16);
+  PROCEDURE Open;
+  PROCEDURE Real(x: REAL; n: INT16);
+  PROCEDURE String(str: ARRAY OF CHAR);
+  PROCEDURE Ten(e: INT16): LONGREAL;
+
+END Out.
+```
 
 Also see [**Compiling**](/doc/Compiling.md).
 
diff --git a/bootstrap/unix-44/OPP.c b/bootstrap/unix-44/OPP.c
index c4ce70c5..ebecc1ea 100644
--- a/bootstrap/unix-44/OPP.c
+++ b/bootstrap/unix-44/OPP.c
@@ -1665,7 +1665,7 @@ static void OPP_Block (OPT_Node *procdec, OPT_Node *statseq)
 				obj->typ = OPT_undftyp;
 				OPP_CheckMark(&obj->vis);
 				if (OPP_sym == 9) {
-					if (((((((((__STRCMP(obj->name, "INTEGER") == 0 || __STRCMP(obj->name, "SHORTINT") == 0) || __STRCMP(obj->name, "LONGINT") == 0) || __STRCMP(obj->name, "HUGEINT") == 0) || __STRCMP(obj->name, "LONGREAL") == 0) || __STRCMP(obj->name, "REAL") == 0) || __STRCMP(obj->name, "CHAR") == 0) || __STRCMP(obj->name, "SET") == 0) || __STRCMP(obj->name, "TRUE") == 0) || __STRCMP(obj->name, "FALSE") == 0) {
+					if (((((((((__STRCMP(obj->name, "SHORTINT") == 0 || __STRCMP(obj->name, "INTEGER") == 0) || __STRCMP(obj->name, "LONGINT") == 0) || __STRCMP(obj->name, "HUGEINT") == 0) || __STRCMP(obj->name, "REAL") == 0) || __STRCMP(obj->name, "LONGREAL") == 0) || __STRCMP(obj->name, "SET") == 0) || __STRCMP(obj->name, "CHAR") == 0) || __STRCMP(obj->name, "TRUE") == 0) || __STRCMP(obj->name, "FALSE") == 0) {
 						OPM_Mark(-310, OPM_curpos);
 					}
 					OPS_Get(&OPP_sym);
diff --git a/bootstrap/unix-48/OPP.c b/bootstrap/unix-48/OPP.c
index c4ce70c5..ebecc1ea 100644
--- a/bootstrap/unix-48/OPP.c
+++ b/bootstrap/unix-48/OPP.c
@@ -1665,7 +1665,7 @@ static void OPP_Block (OPT_Node *procdec, OPT_Node *statseq)
 				obj->typ = OPT_undftyp;
 				OPP_CheckMark(&obj->vis);
 				if (OPP_sym == 9) {
-					if (((((((((__STRCMP(obj->name, "INTEGER") == 0 || __STRCMP(obj->name, "SHORTINT") == 0) || __STRCMP(obj->name, "LONGINT") == 0) || __STRCMP(obj->name, "HUGEINT") == 0) || __STRCMP(obj->name, "LONGREAL") == 0) || __STRCMP(obj->name, "REAL") == 0) || __STRCMP(obj->name, "CHAR") == 0) || __STRCMP(obj->name, "SET") == 0) || __STRCMP(obj->name, "TRUE") == 0) || __STRCMP(obj->name, "FALSE") == 0) {
+					if (((((((((__STRCMP(obj->name, "SHORTINT") == 0 || __STRCMP(obj->name, "INTEGER") == 0) || __STRCMP(obj->name, "LONGINT") == 0) || __STRCMP(obj->name, "HUGEINT") == 0) || __STRCMP(obj->name, "REAL") == 0) || __STRCMP(obj->name, "LONGREAL") == 0) || __STRCMP(obj->name, "SET") == 0) || __STRCMP(obj->name, "CHAR") == 0) || __STRCMP(obj->name, "TRUE") == 0) || __STRCMP(obj->name, "FALSE") == 0) {
 						OPM_Mark(-310, OPM_curpos);
 					}
 					OPS_Get(&OPP_sym);
diff --git a/bootstrap/unix-88/OPP.c b/bootstrap/unix-88/OPP.c
index fbbb2c4a..4db27f7d 100644
--- a/bootstrap/unix-88/OPP.c
+++ b/bootstrap/unix-88/OPP.c
@@ -1665,7 +1665,7 @@ static void OPP_Block (OPT_Node *procdec, OPT_Node *statseq)
 				obj->typ = OPT_undftyp;
 				OPP_CheckMark(&obj->vis);
 				if (OPP_sym == 9) {
-					if (((((((((__STRCMP(obj->name, "INTEGER") == 0 || __STRCMP(obj->name, "SHORTINT") == 0) || __STRCMP(obj->name, "LONGINT") == 0) || __STRCMP(obj->name, "HUGEINT") == 0) || __STRCMP(obj->name, "LONGREAL") == 0) || __STRCMP(obj->name, "REAL") == 0) || __STRCMP(obj->name, "CHAR") == 0) || __STRCMP(obj->name, "SET") == 0) || __STRCMP(obj->name, "TRUE") == 0) || __STRCMP(obj->name, "FALSE") == 0) {
+					if (((((((((__STRCMP(obj->name, "SHORTINT") == 0 || __STRCMP(obj->name, "INTEGER") == 0) || __STRCMP(obj->name, "LONGINT") == 0) || __STRCMP(obj->name, "HUGEINT") == 0) || __STRCMP(obj->name, "REAL") == 0) || __STRCMP(obj->name, "LONGREAL") == 0) || __STRCMP(obj->name, "SET") == 0) || __STRCMP(obj->name, "CHAR") == 0) || __STRCMP(obj->name, "TRUE") == 0) || __STRCMP(obj->name, "FALSE") == 0) {
 						OPM_Mark(-310, OPM_curpos);
 					}
 					OPS_Get(&OPP_sym);
diff --git a/bootstrap/windows-48/OPP.c b/bootstrap/windows-48/OPP.c
index c4ce70c5..ebecc1ea 100644
--- a/bootstrap/windows-48/OPP.c
+++ b/bootstrap/windows-48/OPP.c
@@ -1665,7 +1665,7 @@ static void OPP_Block (OPT_Node *procdec, OPT_Node *statseq)
 				obj->typ = OPT_undftyp;
 				OPP_CheckMark(&obj->vis);
 				if (OPP_sym == 9) {
-					if (((((((((__STRCMP(obj->name, "INTEGER") == 0 || __STRCMP(obj->name, "SHORTINT") == 0) || __STRCMP(obj->name, "LONGINT") == 0) || __STRCMP(obj->name, "HUGEINT") == 0) || __STRCMP(obj->name, "LONGREAL") == 0) || __STRCMP(obj->name, "REAL") == 0) || __STRCMP(obj->name, "CHAR") == 0) || __STRCMP(obj->name, "SET") == 0) || __STRCMP(obj->name, "TRUE") == 0) || __STRCMP(obj->name, "FALSE") == 0) {
+					if (((((((((__STRCMP(obj->name, "SHORTINT") == 0 || __STRCMP(obj->name, "INTEGER") == 0) || __STRCMP(obj->name, "LONGINT") == 0) || __STRCMP(obj->name, "HUGEINT") == 0) || __STRCMP(obj->name, "REAL") == 0) || __STRCMP(obj->name, "LONGREAL") == 0) || __STRCMP(obj->name, "SET") == 0) || __STRCMP(obj->name, "CHAR") == 0) || __STRCMP(obj->name, "TRUE") == 0) || __STRCMP(obj->name, "FALSE") == 0) {
 						OPM_Mark(-310, OPM_curpos);
 					}
 					OPS_Get(&OPP_sym);
diff --git a/bootstrap/windows-88/OPP.c b/bootstrap/windows-88/OPP.c
index fbbb2c4a..4db27f7d 100644
--- a/bootstrap/windows-88/OPP.c
+++ b/bootstrap/windows-88/OPP.c
@@ -1665,7 +1665,7 @@ static void OPP_Block (OPT_Node *procdec, OPT_Node *statseq)
 				obj->typ = OPT_undftyp;
 				OPP_CheckMark(&obj->vis);
 				if (OPP_sym == 9) {
-					if (((((((((__STRCMP(obj->name, "INTEGER") == 0 || __STRCMP(obj->name, "SHORTINT") == 0) || __STRCMP(obj->name, "LONGINT") == 0) || __STRCMP(obj->name, "HUGEINT") == 0) || __STRCMP(obj->name, "LONGREAL") == 0) || __STRCMP(obj->name, "REAL") == 0) || __STRCMP(obj->name, "CHAR") == 0) || __STRCMP(obj->name, "SET") == 0) || __STRCMP(obj->name, "TRUE") == 0) || __STRCMP(obj->name, "FALSE") == 0) {
+					if (((((((((__STRCMP(obj->name, "SHORTINT") == 0 || __STRCMP(obj->name, "INTEGER") == 0) || __STRCMP(obj->name, "LONGINT") == 0) || __STRCMP(obj->name, "HUGEINT") == 0) || __STRCMP(obj->name, "REAL") == 0) || __STRCMP(obj->name, "LONGREAL") == 0) || __STRCMP(obj->name, "SET") == 0) || __STRCMP(obj->name, "CHAR") == 0) || __STRCMP(obj->name, "TRUE") == 0) || __STRCMP(obj->name, "FALSE") == 0) {
 						OPM_Mark(-310, OPM_curpos);
 					}
 					OPS_Get(&OPP_sym);
diff --git a/src/compiler/OPP.Mod b/src/compiler/OPP.Mod
index 29c4fb2e..0ff9b7fb 100644
--- a/src/compiler/OPP.Mod
+++ b/src/compiler/OPP.Mod
@@ -72,8 +72,8 @@ MODULE OPP;  (* NW, RC 6.3.89 / 10.2.94 *)  (* object model 4.12.93 *)
     VAR x: OPT.Node; sf: SYSTEM.INT64;
   BEGIN
     IF sym = OPS.lbrak THEN OPS.Get(sym);
-	  IF ~OPT.SYSimported THEN err(135) END;
-	  ConstExpression(x);
+    IF ~OPT.SYSimported THEN err(135) END;
+    ConstExpression(x);
       IF x^.typ^.form = OPT.Int THEN sf := x^.conval^.intval;
         IF (sf < 0) OR (sf > OPM.MaxSysFlag) THEN err(220); sf := 0 END
       ELSE err(51); sf := 0
@@ -737,7 +737,7 @@ MODULE OPP;  (* NW, RC 6.3.89 / 10.2.94 *)  (* object model 4.12.93 *)
       IF e THEN OPS.Get(sym); StatSeq(y)
       ELSE
          y := NIL;
-	 OPM.Mark(-307, OPM.curpos); (* notice about no OPS.else symbol; -- noch *)
+   OPM.Mark(-307, OPM.curpos); (* notice about no OPS.else symbol; -- noch *)
       END ;
       OPB.Construct(OPT.Ncaselse, cases, y); OPB.Construct(OPT.Ncase, x, cases);
       cases^.conval := OPT.NewConst();
@@ -922,13 +922,17 @@ MODULE OPP;  (* NW, RC 6.3.89 / 10.2.94 *)  (* object model 4.12.93 *)
           OPT.Insert(OPS.name, obj); obj^.mode := OPT.Typ; obj^.typ := OPT.undftyp;
           CheckMark(obj^.vis);
           IF sym = OPS.eql THEN
-		    IF (obj^.name = "INTEGER")  OR (obj^.name = "SHORTINT") OR
-			   (obj^.name = "LONGINT")  OR (obj^.name = "HUGEINT")  OR
-			   (obj^.name = "LONGREAL") OR (obj^.name = "REAL")     OR
-			   (obj^.name = "CHAR")     OR (obj^.name = "SET")      OR
-			   (obj^.name = "TRUE")     OR (obj^.name = "FALSE")    THEN
+            IF (obj^.name = "SHORTINT") OR 
+               (obj^.name = "INTEGER") OR
+               (obj^.name = "LONGINT") OR
+               (obj^.name = "HUGEINT") OR
+               (obj^.name = "REAL") OR
+               (obj^.name = "LONGREAL") OR
+               (obj^.name = "SET") OR
+               (obj^.name = "CHAR") OR
+               (obj^.name = "TRUE") OR (obj^.name = "FALSE") THEN
               OPM.Mark(-310, OPM.curpos); (* notice about aliasing of predefined type *) 
-			END;
+            END;
            OPS.Get(sym); TypeDecl(obj^.typ, obj^.typ)
           ELSIF (sym = OPS.becomes) OR (sym = OPS.colon) THEN
             err(OPS.eql); OPS.Get(sym); TypeDecl(obj^.typ, obj^.typ)