getch,ungetch:implementation

#define BUFSIZE  100

char buf[BUFSIZE];    /*buffer for ungetch */
int bufp =0;          /*next free position in buf */

int getch(void) /*get a (possibly pushed back) character */
{
  return (bufp > 0) ? buf[--bufp]: getchar();
}
void ungetch(int c) /*push character back on input */
{
   if(bufp >=BUFSIZE)
      printf("ungetch:too many characters\n");
   else
     buf[bufp++] =c;
}