diff --git a/src/c99.c b/src/c99.c
index d70c78e..f7873f5 100644
--- a/src/c99.c
+++ b/src/c99.c
@@ -27,7 +27,11 @@
 
 /* private */
 /* types */
-typedef int Prefs;
+typedef struct _Prefs
+{
+	int flags;
+	char const * outfile;
+} Prefs;
 #define PREFS_c 0x1
 #define PREFS_E 0x2
 #define PREFS_g 0x4
@@ -35,69 +39,66 @@ typedef int Prefs;
 
 
 /* prototypes */
-static int _c99(Prefs * prefs, char const * outfile, int filec, char * filev[]);
+static int _c99(Prefs * prefs, int filec, char * filev[]);
 
 
 /* functions */
 /* c99 */
-static int _c99_do(Prefs * prefs, char const * outfile, FILE * outfp,
-		char * infile);
+static int _c99_do(Prefs * prefs, FILE * outfp, char const * infile);
 
-static int _c99(Prefs * prefs, char const * outfile, int filec, char * filev[])
+static int _c99(Prefs * prefs, int filec, char * filev[])
 {
 	FILE * fp;
 	int ret = 0;
 	int i;
 
-	if(outfile != NULL && (fp = fopen(outfile, "w")) == NULL)
-		return error_set_print(PACKAGE, 1, "%s: %s", outfile,
+	if(prefs->outfile != NULL && (fp = fopen(prefs->outfile, "w")) == NULL)
+		return error_set_print(PACKAGE, 1, "%s: %s", prefs->outfile,
 				strerror(errno));
 	for(i = 0; i < filec; i++)
-		ret |= _c99_do(prefs, outfile, fp, filev[i]);
+		ret |= _c99_do(prefs, fp, filev[i]);
 	if(fp != NULL && fclose(fp) != 0)
-		return error_set_print(PACKAGE, 1, "%s: %s", outfile,
+		return error_set_print(PACKAGE, 1, "%s: %s", prefs->outfile,
 				strerror(errno));
 	if(ret != 0)
 		error_print(PACKAGE);
 	return ret;
 }
 
-static int _c99_do_c(Prefs * prefs, char const * outfile, FILE * outfp,
-		char * infile, FILE * infp);
-static int _c99_do_E(Prefs * prefs, char const * outfile, FILE * outfp,
-		char * infile, FILE * infp);
-static int _c99_do_o(Prefs * prefs, char const * outfile, FILE * outfp,
-		char * infile, FILE * infp);
-
-static int _c99_do(Prefs * prefs, char const * outfile, FILE * outfp,
-		char * infile)
+static int _c99_do_c(Prefs * prefs, FILE * outfp, char const * infile,
+		FILE * infp);
+static int _c99_do_E(Prefs * prefs, FILE * outfp, char const * infile,
+		FILE * infp);
+static int _c99_do_o(Prefs * prefs, FILE * outfp, char const * infile,
+		FILE * infp);
+static int _c99_do(Prefs * prefs, FILE * outfp, char const * infile)
 {
 	FILE * infp;
 	int ret;
 
 	if((infp = fopen(infile, "r")) == NULL)
 		return error_set_code(1, "%s: %s", infile, strerror(errno));
-	if(*prefs & PREFS_c)
-		ret = _c99_do_c(prefs, outfile, outfp, infile, infp);
-	else if(*prefs & PREFS_E)
-		ret = _c99_do_E(prefs, outfile, outfp, infile, infp);
+	if(prefs->flags & PREFS_c)
+		ret = _c99_do_c(prefs, outfp, infile, infp);
+	else if(prefs->flags & PREFS_E)
+		ret = _c99_do_E(prefs, outfp, infile, infp);
 	else
-		ret = _c99_do_o(prefs, outfile, outfp, infile, infp);
+		ret = _c99_do_o(prefs, outfp, infile, infp);
 	/* FIXME implement */
 	if(fclose(infp) != 0 && ret == 0)
 		return error_set_code(1, "%s: %s", infile, strerror(errno));
 	return ret;
 }
 
-static int _c99_do_c(Prefs * prefs, char const * outfile, FILE * outfp,
-		char * infile, FILE * infp)
+static int _c99_do_c(Prefs * prefs, FILE * outfp, char const * infile,
+		FILE * infp)
 	/* FIXME outfp should probably be opened only here */
 {
 	int ret = 0;
 	size_t len;
 	char * o = NULL;
 
-	if(outfile == NULL)
+	if(prefs->outfile == NULL)
 	{
 		if((len = strlen(infile)) < 3 || infile[len - 2] != '.'
 				|| infile[len - 1] != 'c')
@@ -122,15 +123,15 @@ static int _c99_do_c(Prefs * prefs, char const * outfile, FILE * outfp,
 	return ret;
 }
 
-static int _c99_do_E(Prefs * prefs, char const * outfile, FILE * outfp,
-		char * infile, FILE * infp)
+static int _c99_do_E(Prefs * prefs, FILE * outfp, char const * infile,
+		FILE * infp)
 {
 	/* FIXME implement */
 	return error_set_code(1, "%s", strerror(ENOSYS));
 }
 
-static int _c99_do_o(Prefs * prefs, char const * outfile, FILE * outfp,
-		char * infile, FILE * infp)
+static int _c99_do_o(Prefs * prefs, FILE * outfp, char const * infile,
+		FILE * infp)
 {
 	/* FIXME implement */
 	return error_set_code(1, "%s", strerror(ENOSYS));
@@ -151,7 +152,6 @@ static int _usage(void)
 int main(int argc, char * argv[])
 {
 	Prefs prefs;
-	char * outfile = NULL;
 	int o;
 
 	memset(&prefs, 0, sizeof(prefs));
@@ -159,26 +159,26 @@ int main(int argc, char * argv[])
 		switch(o)
 		{
 			case 'c':
-				prefs |= PREFS_c;
+				prefs.flags |= PREFS_c;
 				break;
 			case 'E':
-				prefs |= PREFS_E;
+				prefs.flags |= PREFS_E;
 				break;
 			case 'g':
-				prefs |= PREFS_g;
+				prefs.flags |= PREFS_g;
 				break;
 			case 'o':
-				outfile = optarg;
+				prefs.outfile = optarg;
 				break;
 			case 's':
-				prefs |= PREFS_s;
+				prefs.flags |= PREFS_s;
 				break;
 			default:
 				return _usage();
 		}
 	if(optind == argc)
 		return _usage();
-	if(prefs & PREFS_c && outfile != NULL && optind + 1 != argc)
+	if(prefs.flags & PREFS_c && prefs.outfile != NULL && optind + 1 != argc)
 		return _usage();
-	return _c99(&prefs, outfile, argc - optind, &argv[optind]) == 0 ? 0 : 2;
+	return _c99(&prefs, argc - optind, &argv[optind]) == 0 ? 0 : 2;
 }