--- util/igg3d.f.orig	2000-08-06 04:28:16.000000000 +0900
+++ util/igg3d.f	2020-11-21 16:32:17.000000000 +0900
@@ -73,7 +73,7 @@
       INTEGER IGG(MXGRDS)
       CHARACTER*12 CFI
       DATA HEDSIZ/64/,XTEST/1.E30/,XNULL/1.E35/
-      DATA ENDMRK/'80808080'X/
+      DATA ENDMRK/X'80808080'/
 C
       IGF=IKWP('GR3DF',1,IGCF3D(-1))
       COPT=CPP(1,' ')
@@ -615,7 +615,7 @@
       CHARACTER*12 CFF
       REAL*4 GA(NR,NC,NL)
       INTEGER*4 ITAB(*),ITAB2(*),ILEV,IGRID(NR,NC)
-      DATA NULL/'80808080'X/,XTEST/1.E30/,XNULL/1.E35/
+      DATA NULL/X'80808080'/,XTEST/1.E30/,XNULL/1.E35/
       JLEV=ILEV
       DO 1 IR=1,NR
       DO 1 IC=1,NC