diff --git a/CHANGES b/CHANGES
index d18a45c..1506ecd 100644
--- a/CHANGES
+++ b/CHANGES
@@ -212,6 +212,18 @@ Following is the change from calc version 2.11.0t8.9.1 to date:
     is not defined, then calc will use calc_strdup() to simulate
     the real strdup() function.
 
+    Calc no longer makes use of sys_errlist and sys_nerr.  Some systems
+    no longer suppor these values (even though they should from a
+    legacy prospective).  Calc now relies on the fact that strerror()
+    will return NULL of no such system error exists.  System errors >=
+    10000 will be considered calc errors instead.  The Makefile symbol
+    ERRNO_DECL has gone away as well as calc_errno.c and calc_errno.h.
+
+    On system errors are are not known to to the libc strerror() function,
+    strerror() will now print something such as:
+
+	    Unknown error 9999
+
 
 Following is the change from calc version 2.11.0t8 to 2.11.0t8.9:
 
diff --git a/Makefile b/Makefile
index d3ed95b..5d4759b 100644
--- a/Makefile
+++ b/Makefile
@@ -302,39 +302,6 @@ HAVE_STRDUP=
 ALIGN32= -DMUST_ALIGN32
 #ALIGN32= -UMUST_ALIGN32
 
-# On most machines: errno sys_errlist and sys_nerr are declared
-# by either <stdio.h> and/or <errno.h>.  But some systems declare
-# them somewhere else or do not declare them at all!
-#
-# If the system were doing a proper job in headers, this should declare them:
-#
-#	#include <stdio.h>
-#	#include <errno.h>
-#
-# But one some systems one must explicitly declare them as:
-#
-#	extern int errno;
-#	extern const char *const sys_errlist[];
-#	extern int sys_nerr;
-#
-# and on some old systems they must be explicitly and incorrectly declared as:
-#
-#	extern int errno;
-#	extern char *sys_errlist[];
-#	extern int sys_nerr;
-#
-# ERRNO_DECL=			let calc_errno.c determine how to declare them
-# ERRNO_DECL= -DERRNO_NO_DECL	headers declare them correctly
-# ERRNO_DECL= -DERRNO_STD_DECL	one must explicitly declare then
-# ERRNO_DECL= -DERRNO_OLD_DECL	one must explicitly & incorrectly declare them
-#
-# When in doubt, be safe leave ERRNO_DECL empty.
-#
-ERRNO_DECL=
-#ERRNO_DECL= -DERRNO_NO_DECL
-#ERRNO_DECL= -DERRNO_STD_DECL
-#ERRNO_DECL= -DERRNO_OLD_DECL
-
 # where to install binary files
 #
 BINDIR= /usr/local/bin
@@ -942,7 +909,7 @@ BUILD_H_SRC= align32.h args.h calcerr.h conf.h endian_calc.h \
 	fposval.h have_const.h have_fpos.h have_malloc.h \
 	have_memmv.h have_newstr.h have_offscl.h have_posscl.h \
 	have_stdlib.h have_string.h have_times.h have_uid_t.h \
-	have_unistd.h longbits.h longlong.h terminal.h calc_errno.h \
+	have_unistd.h longbits.h longlong.h terminal.h \
 	have_ustat.h have_getsid.h have_getpgid.h \
 	have_gettime.h have_getprid.h have_urandom.h have_rusage.h \
 	have_strdup.h
@@ -957,7 +924,7 @@ BUILD_C_SRC= calcerr.c
 #
 UTIL_C_SRC= align32.c endian.c longbits.c have_newstr.c have_uid_t.c \
 	have_const.c have_stdvs.c have_varvs.c fposval.c have_fpos.c \
-	longlong.c have_offscl.c have_posscl.c have_memmv.c calc_errno.c \
+	longlong.c have_offscl.c have_posscl.c have_memmv.c \
 	have_ustat.c have_getsid.c have_getpgid.c \
 	have_gettime.c have_getprid.c have_rusage.c have_strdup.c
 
@@ -973,20 +940,20 @@ UTIL_MISC_SRC= calcerr_h.sed calcerr_h.awk calcerr_c.sed calcerr_c.awk \
 #
 UTIL_OBJS= endian.o longbits.o have_newstr.o have_uid_t.o \
 	have_const.o fposval.o have_fpos.o longlong.o try_strarg.o \
-	have_stdvs.o have_varvs.o have_posscl.o have_memmv.o calc_errno.o \
+	have_stdvs.o have_varvs.o have_posscl.o have_memmv.o \
 	have_ustat.o have_getsid.o have_getpgid.o \
 	have_gettime.o have_getprid.o ver_calc.o have_rusage.o have_strdup.o
 
 # these temp files may be created (and removed) during the build of BUILD_C_SRC
 #
 UTIL_TMP= ll_tmp fpos_tmp fposv_tmp const_tmp uid_tmp newstr_tmp vs_tmp \
-	calc_errno_tmp memmv_tmp offscl_tmp posscl_tmp newstr_tmp \
+	memmv_tmp offscl_tmp posscl_tmp newstr_tmp \
 	getsid_tmp gettime_tmp getprid_tmp rusage_tmp strdup_tmp
 
 # these utility progs may be used in the process of building BUILD_H_SRC
 #
 UTIL_PROGS= align32 fposval have_uid_t longlong have_const \
-	endian longbits have_newstr have_stdvs have_varvs calc_errno \
+	endian longbits have_newstr have_stdvs have_varvs \
 	have_ustat have_getsid have_getpgid \
 	have_gettime have_getprid ver_calc have_strdup
 
@@ -2288,98 +2255,6 @@ args.h: have_stdvs.c have_varvs.c have_string.h have_unistd.h have_string.h
 	    true; \
 	fi
 
-calc_errno.h: calc_errno.c ${MAKE_FILE}
-	-${Q}rm -f calc_errno.h calc_errno calc_errno_tmp
-	${Q}echo 'forming calc_errno.h'
-	${Q}echo '/*' > calc_errno.h
-	${Q}echo ' * DO NOT EDIT -- generated by the Makefile' >> calc_errno.h
-	${Q}echo ' */' >> calc_errno.h
-	${Q}echo '' >> calc_errno.h
-	${Q}echo '' >> calc_errno.h
-	${Q}echo '#if !defined(__CALC_ERRNO_H__)' >> calc_errno.h
-	${Q}echo '#define __CALC_ERRNO_H__' >> calc_errno.h
-	${Q}echo '' >> calc_errno.h
-	${Q}echo '' >> calc_errno.h
-	-${Q}if [ X"${ERRNO_DECL}" = X"-DERRNO_NO_DECL" ]; then \
-	    echo '/*' >> calc_errno.h; \
-	    echo ' * The calc Makefile explicitly told us' >> calc_errno.h; \
-	    echo ' * how to declare errno and friends.' >> calc_errno.h; \
-	    echo ' */' >> calc_errno.h; \
-	    echo '' >> calc_errno.h; \
-	    echo '#include <stdio.h>' >> calc_errno.h; \
-	    echo '#include <errno.h>' >> calc_errno.h; \
-	elif [ X"${ERRNO_DECL}" = X"-DERRNO_STD_DECL" ]; then \
-	    echo '/*' >> calc_errno.h; \
-	    echo ' * The calc Makefile explicitly told us' >> calc_errno.h; \
-	    echo ' * how to declare errno and friends.' >> calc_errno.h; \
-	    echo ' */' >> calc_errno.h; \
-	    echo '' >> calc_errno.h; \
-	    echo 'extern int errno;			' \
-		 '/* last system error */' >> calc_errno.h; \
-	    echo 'extern const char *const sys_errlist[];' \
-		 ' /* system error messages*/' >> calc_errno.h; \
-	    echo 'extern int sys_nerr;			' \
-		 '/* number of system errors */' >> calc_errno.h; \
-	elif [ X"${ERRNO_DECL}" = X"-DERRNO_OLD_DECL" ]; then \
-	    echo '/*' >> calc_errno.h; \
-	    echo ' * The calc Makefile explicitly told us' >> calc_errno.h; \
-	    echo ' * how to declare errno and friends.' >> calc_errno.h; \
-	    echo ' */' >> calc_errno.h; \
-	    echo '' >> calc_errno.h; \
-	    echo 'extern int errno;		' \
-		 '/* last system error */' >> calc_errno.h; \
-	    echo 'extern char *sys_errlist[];' \
-		 '	 /* system error messages*/' >> calc_errno.h; \
-	    echo 'extern int sys_nerr;		' \
-		 '/* number of system errors */' >> calc_errno.h; \
-	else \
-	    ${LCC} ${ICFLAGS} -DTRY_ERRNO_NO_DECL \
-		  calc_errno.c -o calc_errno 2>calc_errno_tmp; \
-	    if [ -x ./calc_errno ]; then \
-		./calc_errno >> calc_errno.h; \
-	    else \
-		${LCC} ${ICFLAGS} -DTRY_ERRNO_STD_DECL \
-		      calc_errno.c -o calc_errno 2>calc_errno_tmp; \
-		if [ -x ./calc_errno ]; then \
-		    ./calc_errno >> calc_errno.h; \
-		else \
-		    ${LCC} ${ICFLAGS} -DTRY_ERRNO_OLD_DECL \
-			  calc_errno.c -o calc_errno 2>calc_errno_tmp; \
-		    if [ -x ./calc_errno ]; then \
-			./calc_errno >> calc_errno.h; \
-		    else \
-	    echo '/*' >> calc_errno.h; \
-	    echo ' * We were unable to to determine' >> calc_errno.h; \
-	    echo ' * how to declare errno and friends.' >> calc_errno.h; \
-	    echo ' * So we will guess this will work' >> calc_errno.h; \
-	    echo ' * and hope for the best.' >> calc_errno.h; \
-	    echo ' */' >> calc_errno.h; \
-	    echo '' >> calc_errno.h; \
-	    echo 'extern int errno;			' \
-		 '/* last system error */' >> calc_errno.h; \
-	    echo 'extern const char *const sys_errlist[];' \
-		 ' /* system error messages*/' >> calc_errno.h; \
-	    echo 'extern int sys_nerr;			' \
-		 '/* number of system errors */' >> calc_errno.h; \
-		    fi; \
-		fi; \
-	    fi; \
-	fi
-	${Q}echo '' >> calc_errno.h
-	${Q}echo '' >> calc_errno.h
-	${Q}echo '#endif /* !__CALC_ERRNO_H__ */' >> calc_errno.h
-	-${Q}rm -f calc_errno calc_errno_tmp
-	${Q}echo 'calc_errno.h formed'
-	-@if [ -z "${Q}" ]; then \
-	    echo ''; \
-	    echo '=-=-= start of $@ =-=-='; \
-	    cat $@; \
-	    echo '=-=-= end of $@ =-=-='; \
-	    echo ''; \
-	else \
-	    true; \
-	fi
-
 calcerr.h: calcerr.tbl calcerr_h.sed calcerr_h.awk ${MAKE_FILE}
 	-${Q}rm -f calerr.h
 	${Q}echo 'forming calcerr.h'
@@ -2755,7 +2630,6 @@ env:
 	@echo "HAVE_GETPRID=${HAVE_GETPRID}"; echo ""
 	@echo "HAVE_URANDOM=${HAVE_URANDOM}"; echo ""
 	@echo "ALIGN32=${ALIGN32}"; echo ""
-	@echo "ERRNO_DECL=${ERRNO_DECL}"; echo ""
 	@echo "BINDIR=${BINDIR}"; echo ""
 	@echo "TOPDIR=${TOPDIR}"; echo ""
 	@echo "LIBDIR=${LIBDIR}"; echo ""
@@ -3082,6 +2956,8 @@ install: calc libcalc.a ${LIB_H_SRC} ${BUILD_H_SRC} calc.1
 	-rm -f ${LIBDIR}/stdarg.h stdarg.h
 	-rm -f ${LIBDIR}/prototype.h prototype.h
 	-rm -f ${LIBDIR}/libcalcerr.a libcalcerr.a
+	-rm -f ${LIBDIR}/calc_errno.h calc_errno.h ${INCDIRCALC}/calc_errno.h
+	-rm -f calc_errno.c calc_errno.o calc_errno
 	${V} echo '=-=-=-=-= end of $@ rule =-=-=-=-='
 
 ##
@@ -3249,7 +3125,6 @@ calc.o: symbol.h
 calc.o: token.h
 calc.o: value.h
 calc.o: zmath.h
-calc_errno.o: calc_errno.c
 calcerr.o: calcerr.c
 calcerr.o: calcerr.h
 calcerr.o: have_const.h
@@ -3430,7 +3305,6 @@ func.o: alloc.h
 func.o: block.h
 func.o: byteswap.h
 func.o: calc.h
-func.o: calc_errno.h
 func.o: calcerr.h
 func.o: cmath.h
 func.o: config.h
diff --git a/calc_errno.c b/calc_errno.c
deleted file mode 100644
index 6114840..0000000
--- a/calc_errno.c
+++ /dev/null
@@ -1,123 +0,0 @@
-/*
- * errno - Determine how to declare errno, sys_errlist and sys_nerr
- *
- * On most machines: errno sys_errlist and sys_nerr are declared
- * by either <stdio.h> and/or <errno.h>.  But some systems declare
- * them somewhere else or do not declare them at all!
- *
- * If the system were doing a proper job in headers, this should declare them:
- *
- *	#include <stdio.h>
- *	#include <errno.h>
- *
- * But one some systems one must explicitly declare them as:
- *
- *	extern int errno;
- *	extern const char *const sys_errlist[];
- *	extern int sys_nerr;
- *
- * and on some old systems they must be explicitly and incorrectly declared as:
- *
- *	extern int errno;
- *	extern char *sys_errlist[];
- *	extern int sys_nerr;
- *
- * The purpose of this utility is try and find the right way to declare
- * them and to output the middle of a header file called calc_errno.h.
- */
-
-/*
- * Copyright (c) 1999 by Landon Curt Noll.  All Rights Reserved.
- *
- * Permission to use, copy, modify, and distribute this software and
- * its documentation for any purpose and without fee is hereby granted,
- * provided that the above copyright, this permission notice and text
- * this comment, and the disclaimer below appear in all of the following:
- *
- *	supporting documentation
- *	source copies
- *	source works derived from this source
- *	binaries derived from this source or from derived source
- *
- * LANDON CURT NOLL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
- * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO
- * EVENT SHALL LANDON CURT NOLL BE LIABLE FOR ANY SPECIAL, INDIRECT OR
- * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF
- * USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
- * OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
- * PERFORMANCE OF THIS SOFTWARE.
- *
- * chongo was here	/\../\
- */
-
-#include <stdio.h>
-#if defined(TRY_ERRNO_NO_DECL)
-#  include <errno.h>
-#endif /* TRY_ERRNO_NO_DECL */
-
-int
-main(void)
-{
-
-#if defined(TRY_ERRNO_NO_DECL)
-	printf("/*\n");
-	printf(" * The following comments were produced by calc_errno\n");
-	printf(" * in an effort to see if these values were correctly\n");
-	printf(" * declared when calc_errno.c was compiled.\n");
-	printf(" */\n\n");
-	printf("/* Initially errno is %d */\n", errno);
-	printf("/* There are %d entries in sys_errlist[] */\n", sys_nerr);
-	printf("/* The 2nd sys_errlist entry is \"%s\" */\n\n", sys_errlist[1]);
-	printf("/*\n");
-	printf(" * Based on the above, calc_errno now knows\n");
-	printf(" * how to declare errno and friends.\n");
-	printf(" */\n\n");
-	printf("#include <stdio.h>\n");
-	printf("#include <errno.h>\n");
-#elif defined(TRY_ERRNO_OLD_DECL)
-	extern int errno;		/* last system error */
-	extern char *sys_errlist[];	/* system error messages */
-	extern int sys_nerr;		/* number of system errors*/
-
-	printf("/*\n");
-	printf(" * The following comments were produced by calc_errno\n");
-	printf(" * in an effort to see if these values were correctly\n");
-	printf(" * declared when calc_errno.c was compiled.\n");
-	printf(" */\n\n");
-	printf("/* Initially errno is %d */\n", errno);
-	printf("/* There are %d entries in sys_errlist[] */\n", sys_nerr);
-	printf("/* The 2nd sys_errlist entry is \"%s\" */\n\n", sys_errlist[1]);
-	printf("/*\n");
-	printf(" * Based on the above, calc_errno now knows\n");
-	printf(" * how to declare errno and friends.\n");
-	printf(" */\n\n");
-	printf("extern int errno;\t\t/* last system error */\n");
-	printf("extern char *sys_errlist[];\t"
-	       "/* system error messages */\n");
-	printf("extern int sys_nerr;\t\t/* number of system errors*/\n");
-#else	/* assume defined(TRY_ERRNO_STD_DECL) */
-	extern int errno;			/* last system error */
-	extern const char *const sys_errlist[];	/* system error messages */
-	extern int sys_nerr;			/* number of system errors*/
-
-	printf("/*\n");
-	printf(" * The following comments were produced by calc_errno\n");
-	printf(" * in an effort to see if these values were correctly\n");
-	printf(" * declared when calc_errno.c was compiled.\n");
-	printf(" */\n\n");
-	printf("/* Initially errno is %d */\n", errno);
-	printf("/* There are %d entries in sys_errlist[] */\n", sys_nerr);
-	printf("/* The 2nd sys_errlist entry is \"%s\" */\n\n", sys_errlist[1]);
-	printf("/*\n");
-	printf(" * Based on the above, calc_errno now knows\n");
-	printf(" * how to declare errno and friends.\n");
-	printf(" */\n\n");
-	printf("extern int errno;\t\t\t/* last system error */\n");
-	printf("extern const char *const sys_errlist[];\t"
-	       "/* system error messages */\n");
-	printf("extern int sys_nerr;\t\t\t/* number of system errors*/\n");
-#endif
-
-	/* exit(0); */
-	return 0;
-}
diff --git a/func.c b/func.c
index 1376224..bf3d896 100644
--- a/func.c
+++ b/func.c
@@ -10,6 +10,7 @@
 #include <stdio.h>
 #include <ctype.h>
 #include <sys/types.h>
+#include <errno.h>
 
 #if defined(FUNCLIST)
 
@@ -17,8 +18,6 @@
 
 #else /* FUNCLIST */
 
-#include "calc_errno.h"
-
 #include "have_unistd.h"
 #if defined(HAVE_UNISTD_H)
 #include <unistd.h>
@@ -29,16 +28,24 @@
 #include <stdlib.h>
 #endif
 
+#include "have_string.h"
+#if defined(HAVE_STRING_H)
+#include <string.h>
+#endif
+
 #include "have_times.h"
 #if defined(HAVE_TIME_H)
 #include <time.h>
 #endif
+
 #if defined(HAVE_TIMES_H)
 #include <times.h>
 #endif
+
 #if defined(HAVE_SYS_TIME_H)
 #include <sys/time.h>
 #endif
+
 #if defined(HAVE_SYS_TIMES_H)
 #include <sys/times.h>
 #endif
@@ -4628,6 +4635,7 @@ f_strerror(int count, VALUE **vals)
 	long i;
 	char *cp;
 
+	/* parse args */
 	if (count > 0) {
 		vp = vals[0];
 		if (vp->v_type < 0) {
@@ -4639,36 +4647,44 @@ f_strerror(int count, VALUE **vals)
 			if (i < 0 || i > 32767)
 				return error_value(E_STRERROR2);
 		}
-	}
-	else
+	} else {
 		i = set_errno(-1);
+	}
 
+	/* setup return type */
 	result.v_type = V_STR;
 
+	/* change the meaning of error 0 */
 	if (i == 0)
 		i = E__BASE;
 
+	/* firewall - return generic error string if it is not assigned */
 	if (i >= nexterrnum || (i > E__HIGHEST && i < E_USERDEF)
-			|| (i < E__BASE && i >= sys_nerr)) {
-		cp = (char *) malloc(12);
+			|| (i < E__BASE && strerror(i) == NULL)) {
+		cp = (char *) malloc(sizeof("Error 1234567890")+1);
 		if (cp == NULL) {
 			math_error("Out of memory for strerror");
 			/*NOTREACHED*/
 		}
-		sprintf(cp, "Error %ld", i);
+		sprintf(cp, "Unknown error %ld", i);
 		result.v_str = makestring(cp);
 		return result;
 	}
 
-	if (i < E__BASE)		/* system error */
-		cp = (char *) sys_errlist[i];
+	/* system error */
+	if (i < E__BASE) {
+		cp = strerror(i);
 
-	else if (i >= E_USERDEF)	/* user-described error */
+	/* user-described error */
+	} else if (i >= E_USERDEF) {
 		cp = namestr(&newerrorstr, i - E_USERDEF);
 
-	else				/* calc-described error */
+	/* calc-described error */
+	} else {
 		cp = (char *)error_table[i - E__BASE];
+	}
 
+	/* return result as a V_STR */
 	result.v_str = makenewstring(cp);
 	return result;
 }
diff --git a/lib/regress.cal b/lib/regress.cal
index 7d991e2..317f3e8 100644
--- a/lib/regress.cal
+++ b/lib/regress.cal
@@ -2871,7 +2871,7 @@ print '053: parsed test_frem()';
  */
 define test_error()
 {
-	local strx, e99, list1, e999;
+	local strx, e99, list1, e9999;
 	local a, b, c, n, x;		/* used by newerror() */
 
 	print '3600: Beginning test_error';
@@ -3044,11 +3044,12 @@ define test_error()
 					'3710: newerror() == newerror("???")');
 	vrfy(newerror("") == newerror(),
 					'3711: newerror("") == newerror()');
-	e999 = error(999);
-	print				'3712: e999 = error(999)';
-	vrfy(errno() == 999,		'3713: errno() == 999');
-	vrfy(error() == e999,		'3714: error() == e999');
-	vrfy(strerror() == "Error 999",	'3715: strerror() == "Error 999"');
+	e9999 = error(9999);
+	print				'3712: e9999 = error(9999)';
+	vrfy(errno() == 9999,		'3713: errno() == 9999');
+	vrfy(error() == e9999,		'3714: error() == e9999');
+	vrfy(strerror() == "Unknown error 9999",
+				'3715: strerror() == "Unknown error 9999"');
 	x = newerror("Alpha");
 	print				'3716: x = newerror("Alpha")';
 	n = iserror(x);
@@ -3056,10 +3057,11 @@ define test_error()
 	vrfy(errno() == n,		'3718: errno() == n');
 	vrfy(error() == x,		'3719: error() == x');
 	vrfy(strerror() == "Alpha",	'3720: strerror() == "Alpha"');
-	vrfy(errno(999) == n,		'3721: errno() == n');
-	vrfy(errno() == 999,		'3722: errno() == 999');
-	vrfy(error() == e999,		'3723: error() == e999');
-	vrfy(strerror() == "Error 999",	'3724: strerror() == "Error 999"');
+	vrfy(errno(9999) == n,		'3721: errno() == n');
+	vrfy(errno() == 9999,		'3722: errno() == 9999');
+	vrfy(error() == e9999,		'3723: error() == e9999');
+	vrfy(strerror() == "Unknown error 9999",
+				'3724: strerror() == "Unknown error 9999"');
 	a = 1/0;
 	print				'3725: a = 1/0';
 	vrfy(strerror() == "Division by zero",
diff --git a/value.c b/value.c
index a882a71..1042265 100644
--- a/value.c
+++ b/value.c
@@ -22,8 +22,6 @@
 
 #define LINELEN 80		/* length of a typical tty line */
 
-extern int sys_nerr;
-
 /*
  * Free a value and set its type to undefined.
  *
@@ -2694,7 +2692,7 @@ printvalue(VALUE *vp, int flags)
 	if (type < 0) {
 		if (userfunc("error_print", vp))
 			return;
-		if (-type >= sys_nerr)
+		if (-type >= E__BASE)
 			printf("Error %d", -type);
 		else
 			printf("System error %d", -type);
diff --git a/version.c b/version.c
index f36f2f4..4bb5c95 100644
--- a/version.c
+++ b/version.c
@@ -18,7 +18,7 @@ static char *program;
 #define MAJOR_VER	2	/* major version */
 #define MINOR_VER	11	/* minor version */
 #define MAJOR_PATCH	0	/* patch level or 0 if no patch */
-#define MINOR_PATCH	"9.4.2"	/* test number or empty string if no patch */
+#define MINOR_PATCH	"9.4.3"	/* test number or empty string if no patch */
 
 /*
  * calc version constants