extern int fileno(FILE *stream);
extern size_t fread(void *buf, size_t size, size_t n, FILE *fp);
-extern size_t fwrite(void *buf, size_t size, size_t n, FILE *fp);
+extern size_t fwrite(const void *buf, size_t size, size_t n, FILE *fp);
extern int fgetc(FILE *fp);
+extern char *fgets(char *s, int size, FILE *fp);
extern int fputc(int ch, FILE *fp);
+extern int fputs(const char *s, FILE *fp);
extern int getchar(void);
extern int putchar(int ch);