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);
extern int fprintf(FILE *fp, const char *format, ...);
extern int vfprintf(FILE *fp, const char *format, va_list args);
+// scanf
+extern int scanf(const char *format, ...);
+extern int fscanf(FILE *stream, const char *format, ...);
+extern int sscanf(const char *str, const char *format, ...);
+extern int vscanf(const char *format, va_list ap);
+extern int vsscanf(const char *str, const char *format, va_list ap);
+extern int vfscanf(FILE *stream, const char *format, va_list ap);
+
extern FILE *stdin;
extern FILE *stdout;
extern FILE *stderr;