diff -urp mathgl-2.3.3/examples/full_test.cpp mathgl-2.3.3-signed_char/examples/full_test.cpp
--- mathgl-2.3.3/examples/full_test.cpp	2015-11-24 12:36:50.209458320 +0600
+++ mathgl-2.3.3-signed_char/examples/full_test.cpp	2015-11-26 11:45:03.816885186 +0600
@@ -392,7 +392,7 @@ int main(int argc,char **argv)
 	mgl_suppress_warn(true);
 	const char *suf = "";
 	char name[256]="", *tmp;
-	int ch;
+	signed int ch;
 	time_t st,en;	time(&st);
 	mglGraph *gr = NULL;
 	mglSample *s=samp;
diff -urp mathgl-2.3.3/utils/make_bin.cpp mathgl-2.3.3-signed_char/utils/make_bin.cpp
--- mathgl-2.3.3/utils/make_bin.cpp	2015-11-24 12:36:50.209458320 +0600
+++ mathgl-2.3.3-signed_char/utils/make_bin.cpp	2015-11-26 11:44:23.629270158 +0600
@@ -24,7 +24,7 @@ int main(int argc, char *argv[])
 {
 	mglFont fnt;
 	std::string path, base, fname;
-	char ch;
+	signed char ch;
 
 	while(1)
 	{
diff -urp mathgl-2.3.3/utils/mglconv.cpp mathgl-2.3.3-signed_char/utils/mglconv.cpp
--- mathgl-2.3.3/utils/mglconv.cpp	2015-11-24 12:36:50.209458320 +0600
+++ mathgl-2.3.3-signed_char/utils/mglconv.cpp	2015-11-26 11:47:02.414797998 +0600
@@ -28,7 +28,8 @@ int main(int argc, char *argv[])
 	mgl_suppress_warn(true);
 	mglGraph gr;
 	mglParse p(true);
-	char ch, buf[2048], iname[256]="", oname[256]="";
+	signed char ch;
+	char buf[2048], iname[256]="", oname[256]="";
 	std::vector<std::wstring> var;
 	std::wstring str;
 	bool none=false;
diff -urp mathgl-2.3.3/utils/mglview.cpp mathgl-2.3.3-signed_char/utils/mglview.cpp
--- mathgl-2.3.3/utils/mglview.cpp	2015-11-24 12:36:50.209458320 +0600
+++ mathgl-2.3.3-signed_char/utils/mglview.cpp	2015-11-26 11:46:16.959364509 +0600
@@ -39,7 +39,8 @@ int show(mglGraph *gr)
 //-----------------------------------------------------------------------------
 int main(int argc, char **argv)
 {
-	char ch, iname[256]="";
+	signed char ch;
+	char iname[256]="";
 	mgl_suppress_warn(true);
 	while(1)
 	{