#ifndef __SDC51_STDLIB_H
#define __SDC51_STDLIB_H 1
-#ifndef
+#ifndef NULL
# define NULL (void *)0
#endif
+#include <malloc.h>
+
+int abs(int j);
+long int labs(long int j);
+
+extern float atof (char *);
extern int atoi (char *);
extern long atol (char *);