diff --git a/x_ctypes/src/x_ctypes.c b/x_ctypes/src/x_ctypes.c
index f49da04..f1d1cd7 100644
--- a/x_ctypes/src/x_ctypes.c
+++ b/x_ctypes/src/x_ctypes.c
@@ -11,3 +11,14 @@ int x_isdigit(const char x){
 	return 0;
 }
 
+int x_isnumber(const char* str){
+	const char * ptr;
+
+	for (ptr = str; *ptr != '\0'; ptr++){
+		if ( !x_isdigit(*ptr) ){
+			return 0;
+		}
+	}
+
+	return 1;
+}
diff --git a/x_ctypes/src/x_ctypes.h b/x_ctypes/src/x_ctypes.h
index 3d08dab..9cb5141 100644
--- a/x_ctypes/src/x_ctypes.h
+++ b/x_ctypes/src/x_ctypes.h
@@ -4,5 +4,6 @@
 
 // returns 0 if x is not a digit and 1 if it is
 int x_isdigit(char x);
+int x_isnumber(char *str);
 
 #endif