diff --git a/src/compiler/OPM.Mod b/src/compiler/OPM.Mod
index 5635fa03..44d9ff6f 100755
--- a/src/compiler/OPM.Mod
+++ b/src/compiler/OPM.Mod
@@ -754,13 +754,30 @@ MODULE OPM;  (* RC 6.3.89 / 28.6.89, J.Templ 10.7.89 / 22.7.96  *)
     END;
   END WriteInt;
 
+  (* r with 17 significant digits, which read back as the same double: 15 digits lost precision,
+     and very small values (as LowLReal.small) came out as 0 *)
+  PROCEDURE -AAincludeStdio '#include <stdio.h>';
+  PROCEDURE -FormatReal(buf: SYSTEM.ADDRESS; r: LONGREAL) 'snprintf((char*)(ADDRESS)(buf), 40, "%.17g", r)';
+
+  PROCEDURE WriteExactReal(r: LONGREAL);
+    VAR s: ARRAY 40 OF CHAR; i: INTEGER; real: BOOLEAN;
+  BEGIN
+    FormatReal(SYSTEM.ADR(s), r);
+    i := 0; real := FALSE;
+    WHILE s[i] # 0X DO IF (s[i] = ".") OR (s[i] = "e") THEN real := TRUE END; INC(i) END;
+    IF ~real THEN s[i] := "."; s[i+1] := "0"; s[i+2] := 0X END;  (* not an integer constant in C *)
+    WriteStringVar(s)
+  END WriteExactReal;
+
   PROCEDURE WriteReal* (r: LONGREAL; suffx: CHAR);
     VAR W: Texts.Writer; T: Texts.Text; R: Texts.Reader; s: ARRAY 32 OF CHAR; ch: CHAR; i: INTEGER;
   BEGIN
-(*should be improved *)
     IF (r < SignedMaximum(LongintSize)) & (r > SignedMinimum(LongintSize)) & (r = ENTIER(r)) THEN
       IF suffx = "f" THEN WriteString("(REAL)") ELSE WriteString("(LONGREAL)") END ;
       WriteInt(ENTIER(r))
+    ELSIF SYSTEM.VAL(SYSTEM.INT64, r) DIV 10000000000000H MOD 800H # 7FFH THEN  (* not inf or nan *)
+      IF suffx = "f" THEN WriteString("(REAL)") ELSE WriteString("(LONGREAL)") END ;
+      WriteExactReal(r)
     ELSE
       Texts.OpenWriter(W);
       IF suffx = "f" THEN Texts.WriteLongReal(W, r, 16) ELSE Texts.WriteLongReal(W, r, 23) END ;
@@ -895,9 +912,17 @@ MODULE OPM;  (* RC 6.3.89 / 28.6.89, J.Templ 10.7.89 / 22.7.96  *)
 
 
 
+  (* the largest REAL and LONGREAL, from their bits: 1.7976931348623157D307 * 9.999999 was
+     1.79769296342094D308, and older compilers refuse the exponent 308 *)
+  PROCEDURE SetMaxReals;
+    VAR i32: SYSTEM.INT32; i64: SYSTEM.INT64; r: REAL;
+  BEGIN
+    i32 := 7F7FFFFFH; r := SYSTEM.VAL(REAL, i32); MaxReal := r;
+    i64 := 7FEFFFFFFFFFFFFFH; MaxLReal := SYSTEM.VAL(LONGREAL, i64)
+  END SetMaxReals;
+
 BEGIN
-  MaxReal := 3.40282346D38;                      (* REAL is 4 bytes *)
-  MaxLReal := 1.7976931348623157D307 * 9.999999; (* LONGREAL is 8 bytes, should be 1.7976931348623157D308 *)
+  SetMaxReals;
   MinReal  := -MaxReal;
   MinLReal := -MaxLReal;
   FindInstallDir;
diff --git a/src/compiler/OPS.Mod b/src/compiler/OPS.Mod
index f81bcae6..be08ede4 100644
--- a/src/compiler/OPS.Mod
+++ b/src/compiler/OPS.Mod
@@ -89,20 +89,15 @@ MODULE OPS;  (* NW, RC 6.3.89 / 18.10.92 *)    (* object model 3.6.92 *)
     name[i] := 0X; sym := ident
   END Identifier;
 
+  (* the decimal constants of the scanner, correctly rounded by the C library *)
+  PROCEDURE -Astdlib '#include <stdlib.h>';
+  PROCEDURE -strtod(s: SYSTEM.ADDRESS): LONGREAL '(LONGREAL)strtod((const char*)(ADDRESS)(s), 0)';
+  PROCEDURE -strtof(s: SYSTEM.ADDRESS): REAL '(REAL)strtof((const char*)(ADDRESS)(s), 0)';
+
   PROCEDURE Number;
     CONST maxhexdigits = 16;
-    VAR i, m, n, d, e: INTEGER; dig: ARRAY 24 OF CHAR; f: LONGREAL; expCh: CHAR; neg: BOOLEAN;
-
-    PROCEDURE Ten(e: INTEGER): LONGREAL;
-      VAR x, p: LONGREAL;
-    BEGIN x := 1; p := 10;
-      WHILE e > 0 DO
-        IF ODD(e) THEN x := x*p END;
-        e := e DIV 2;
-        IF e > 0 THEN p := p*p END (* prevent overflow *)
-      END;
-      RETURN x
-    END Ten;
+    VAR i, m, n, d, e, k, j: INTEGER; dig: ARRAY 40 OF CHAR; f: LONGREAL; expCh: CHAR; neg: BOOLEAN;
+      num: ARRAY 64 OF CHAR; exp: ARRAY 8 OF CHAR;
 
     PROCEDURE Ord(ch: CHAR; hex: BOOLEAN): INTEGER;
     BEGIN (* ("0" <= ch) & (ch <= "9") OR ("A" <= ch) & (ch <= "F") *)
@@ -153,6 +148,8 @@ MODULE OPS;  (* NW, RC 6.3.89 / 18.10.92 *)    (* object model 3.6.92 *)
       END
     ELSE (* fraction *)
       f := 0; e := 0; expCh := "E";
+      num[0] := "0"; num[1] := "."; k := 2; j := 0;  (* "0.digits" for strtod, with "e" exp below *)
+      WHILE j < n DO num[k] := dig[j]; INC(k); INC(j) END;
       WHILE n > 0 DO (* 0 <= f < 1 *) DEC(n); f := (Ord(dig[n], FALSE) + f)/10 END;
       IF (ch = "E") OR (ch = "D") THEN expCh := ch; OPM.Get(ch); neg := FALSE;
         IF ch = "-" THEN neg := TRUE; OPM.Get(ch)
@@ -169,20 +166,18 @@ MODULE OPS;  (* NW, RC 6.3.89 / 18.10.92 *)    (* object model 3.6.92 *)
         END
       END;
       DEC(e, i-d-m); (* decimal point shift *)
+      num[k] := "e"; INC(k); IF e < 0 THEN num[k] := "-"; INC(k) END;
+      j := ABS(e); n := 0; REPEAT exp[n] := CHR(ORD("0") + j MOD 10); j := j DIV 10; INC(n) UNTIL j = 0;
+      WHILE n > 0 DO DEC(n); num[k] := exp[n]; INC(k) END;
+      num[k] := 0X;
+      (* the range is that of the result: infinite, or 0 from digits that are not, is too large
+         (was: the decimal exponent within MaxRExp, MaxLExp, which refused 1.17549435E-38) *)
       IF expCh = "E" THEN numtyp := real;
-        IF (1-OPM.MaxRExp < e) & (e <= OPM.MaxRExp) THEN
-          IF e < 0 THEN realval := SHORT(f / Ten(-e))
-          ELSE realval := SHORT(f * Ten(e))
-          END
-        ELSE err(203)
-        END
+        IF (e > -400) & (e < 400) THEN realval := strtof(SYSTEM.ADR(num)) ELSE realval := 0 END;
+        IF (realval > MAX(REAL)) OR (realval = 0) & (m > 0) THEN err(203) END
       ELSE numtyp := longreal;
-        IF (1-OPM.MaxLExp < e) & (e <= OPM.MaxLExp) THEN
-          IF e < 0 THEN lrlval := f / Ten(-e)
-          ELSE lrlval := f * Ten(e)
-          END
-        ELSE err(203)
-        END
+        IF (e > -400) & (e < 400) THEN lrlval := strtod(SYSTEM.ADR(num)) ELSE lrlval := 0 END;
+        IF (lrlval > MAX(LONGREAL)) OR (lrlval = 0) & (m > 0) THEN err(203) END
       END
     END
   END Number;
diff --git a/src/test/confidence/out/expected b/src/test/confidence/out/expected
index dab1e079..cb43b5e3 100644
--- a/src/test/confidence/out/expected
+++ b/src/test/confidence/out/expected
@@ -6,7 +6,7 @@ Real number hex representation.
 -1.1D0:                BFF199999999999A
  1.1D3:                4091300000000000
  1.1D-3:               3F5205BC01A36E2F
- 1.2345678987654321D3: 40934A45874103D8
+ 1.2345678987654321D3: 40934A45874103E1
  0.0:                  0000000000000000
  0.000123D0:           3F201F31F46ED246
  1/0.0:                7FF0000000000000
@@ -68,7 +68,7 @@ Testing LONGREAL.
 -1.1D0:                                -1.1000000000000000D+000
  1.1D3:                                 1.1000000000000000D+003
  1.1D-3:                                1.1000000000000000D-003
- 1.2345678987654321D3:                  1.2345678987654300D+003
+ 1.2345678987654321D3:                  1.2345678987654320D+003
  0.0:                                   0.0000000000000000D+000
  0.000123D0:                            1.2300000000000000D-004
  1/0.0:                                                Infinity
@@ -134,7 +134,7 @@ Real number hex representation.
 -1.1D0:                BFF199999999999A
  1.1D3:                4091300000000000
  1.1D-3:               3F5205BC01A36E2F
- 1.2345678987654321D3: 40934A45874103D8
+ 1.2345678987654321D3: 40934A45874103E1
  0.0:                  0000000000000000
  0.000123D0:           3F201F31F46ED246
  1/0.0:                7FF0000000000000
@@ -196,7 +196,7 @@ Testing LONGREAL.
 -1.1D0:                                -1.1000000000000000D+000
  1.1D3:                                 1.1000000000000000D+003
  1.1D-3:                                1.1000000000000000D-003
- 1.2345678987654321D3:                  1.2345678987654300D+003
+ 1.2345678987654321D3:                  1.2345678987654320D+003
  0.0:                                   0.0000000000000000D+000
  0.000123D0:                            1.2300000000000000D-004
  1/0.0:                                                Infinity
diff --git a/src/test/confidence/planned-binary-change b/src/test/confidence/planned-binary-change
index 9135bbd2..ceba94ea 100644
--- a/src/test/confidence/planned-binary-change
+++ b/src/test/confidence/planned-binary-change
@@ -1 +1 @@
-18 Dec 2016 16:55:53
+Tue Oct  6 20:11:12 +04 2026