Correction: function names must be ft_*

ft_isdigit_test.c

@@ -0,0 +1,13 @@
+#include "libft.h"
+#include<stdio.h>
+
+int	main(void)
+{
+	int c;
+
+	for (c = 0; c < 256; c++)
+	{
+		printf("'%c' (%i); isdigit(c): %i\r\n", c, c, ft_isdigit(c));
+	}
+	return (0);
+}