long decin (void) {
        int character;          /* ASCII input from the user */
        long digit;             /* each digit as it is found */
        long sum = 0;           /* accumulated number */

        /* input terminates with a non-digit character */
        while (isdigit (character = getchar())) {

                /* change from ASCII */
                digit = character & ~ASCII_ZERO;

                /* accumulate number */
                sum *= 10;
                sum += digit;
        }

        /* return non-digit to input stream */
        ungetc (character, stdin);

        /* result found */
        return sum;