#include <stdio.h>
int getc(FILE *fp);
int fgetc(FILE *fp);
int getchar(void);
int ungetc(int c, FILE *fp);

#include <wchar.h>
wint_t getwc(FILE *fp);
wint_t fgetwc(FILE *fp);
wint_t ungetwc(wchar_t c, FILE *fp);

#include <wchar.h>
wint_t getwchar(void);

getc and fgetc each read a single byte from the input stream fp. It is converted to unsigned char, and then returned as int. If the stream was already at its end, the functions set the end-of-file indicator, and return EOF.

Similarly, getwc and fgetwc each read a single wide character from the input stream fp. It is converted to wint_t and returned. If the stream was already at its end, the functions set the end-of-file indicator, and return WEOF.

If getc or getwc is a macro, it might evaluate its argument more than once, so don't use expressions with side effects as arguments to these functions. fgetc and fgetwc are guaranteed not to do this.

getchar() is equivalent to getc(stdin). getwchar() is equivalent to getwc(stdin).

ungetc and ungetwc push the byte or character c back onto the input stream fp so that it will be read as the next byte or character. At most one byte or character is guaranteed to be able to be pushed back before being read again. To push back a char, convert it to unsigned char before passing it to ungetc, e.g., ungetc((unsigned char) c, stdin). ungetc returns c on success, and EOF on error. ungetwc returns WEOF if c is WEOF or an invalid wide character.

The functions getc, fgetc, getchar and ungetc are byte-oriented. The functions getwc, fgetwc, getwchar and ungetwc are wide-oriented.