c语言编写程序，用结构体类型实现复数的加、减、乘、除运算，每种运算用函数完成。

可以使用以下代码实现：

#include <stdio.h>

typedef struct {
    double real;
    double imag;
} Complex;

Complex add(Complex a, Complex b) {
    Complex result;
    result.real = a.real + b.real;
    result.imag = a.imag + b.imag;
    return result;
}

Complex sub(Complex a, Complex b) {
    Complex result;
    result.real = a.real - b.real;
    result.imag = a.imag - b.imag;
    return result;
}

Complex mul(Complex a, Complex b) {
    Complex result;
    result.real = a.real * b.real - a.imag * b.imag;
    result.imag = a.real * b.imag + a.imag * b.real;
    return result;
}

Complex div(Complex a, Complex b) {
    Complex result;
    double denominator = b.real * b.real + b.imag * b.imag;
    result.real = (a.real * b.real + a.imag * b.imag) / denominator;
    result.imag = (a.imag * b.real - a.real * b.imag) / denominator;
    return result;
}

int main() {
    Complex a = {1.0, 2.0};
    Complex b = {3.0, 4.0};
    Complex c = add(a, b);
    printf("a + b = %.2f + %.2fi\n", c.real, c.imag);
    c = sub(a, b);
    printf("a - b = %.2f + %.2fi\n", c.real, c.imag);
    c = mul(a, b);
    printf("a * b = %.2f + %.2fi\n", c.real, c.imag);
    c = div(a, b);
    printf("a / b = %.2f + %.2fi\n", c.real, c.imag);
    return 0;
}

这个程序定义了一个复数结构体，然后实现了加、减、乘、除四种运算的函数。在主函数中，我们定义了两个复数，然后分别调用这四个函数，输出结果。