ungetc() is an I/O function that push character back into an input stream at the same position to the same position. This will be obtained by the next read operation on the stream. This function returns the character that was pushed back, otherwise EOF is returned.

    int ungetc( int character, FILE * stream );

   #include <stdio.h>
   #include <ctype.h>
   int main(void)
     {
       int a=0;
       char ch;
       puts("Enter an integer followed by a char:");
       while((ch = getchar()) != EOF && isdigit(ch))
        a = 10 * a + ch - 48; 
        if (ch != EOF)
          ungetc(ch, stdin);
        printf("First character is  %d, next char 
               entered is  = %c\n", a, getchar());
        return 0;
     }

   Enter an integer then a char:
   2e
   First character is 2, next character entered is e

In the above example the "ungetc()" is used to find the integer, pushed the char to be entered.