设计并上机实现抽象数据类型“有理数”，有理数的基本操作包括：两个有理数的加、减、乘、除等（包括有理数的创建和输出）。

好的，我可以回答这个问题。有理数可以用分子和分母表示，我们可以设计一个结构体来表示有理数，其中分子和分母都是整数类型。有理数的加、减、乘、除等操作可以通过分别对分子和分母进行运算来实现。具体实现可以参考以下代码：

#include <stdio.h>

typedef struct {
    int numerator;  // 分子
    int denominator;  // 分母
} Rational;

// 求最大公约数
int gcd(int a, int b) {
    return b ==  ? a : gcd(b, a % b);
}

// 化简有理数
void simplify(Rational *r) {
    int g = gcd(r->numerator, r->denominator);
    r->numerator /= g;
    r->denominator /= g;
}

// 有理数加法
Rational add(Rational r1, Rational r2) {
    Rational result;
    result.numerator = r1.numerator * r2.denominator + r2.numerator * r1.denominator;
    result.denominator = r1.denominator * r2.denominator;
    simplify(&result);
    return result;
}

// 有理数减法
Rational subtract(Rational r1, Rational r2) {
    Rational result;
    result.numerator = r1.numerator * r2.denominator - r2.numerator * r1.denominator;
    result.denominator = r1.denominator * r2.denominator;
    simplify(&result);
    return result;
}

// 有理数乘法
Rational multiply(Rational r1, Rational r2) {
    Rational result;
    result.numerator = r1.numerator * r2.numerator;
    result.denominator = r1.denominator * r2.denominator;
    simplify(&result);
    return result;
}

// 有理数除法
Rational divide(Rational r1, Rational r2) {
    Rational result;
    result.numerator = r1.numerator * r2.denominator;
    result.denominator = r1.denominator * r2.numerator;
    simplify(&result);
    return result;
}

// 输出有理数
void printRational(Rational r) {
    printf("%d/%d\n", r.numerator, r.denominator);
}

int main() {
    Rational r1 = {1, 2};
    Rational r2 = {3, 4};
    Rational r3 = add(r1, r2);
    Rational r4 = subtract(r1, r2);
    Rational r5 = multiply(r1, r2);
    Rational r6 = divide(r1, r2);
    printRational(r3);
    printRational(r4);
    printRational(r5);
    printRational(r6);
    return ;
}