在C語言中，可以使用結構體來表示復數，并定義相應的運算函數來處理復數的浮點運算。以下是一個簡單的示例代碼：

#include <stdio.h>

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

Complex add(Complex c1, Complex c2) {
    Complex result;
    result.real = c1.real + c2.real;
    result.imag = c1.imag + c2.imag;
    return result;
}

Complex subtract(Complex c1, Complex c2) {
    Complex result;
    result.real = c1.real - c2.real;
    result.imag = c1.imag - c2.imag;
    return result;
}

Complex multiply(Complex c1, Complex c2) {
    Complex result;
    result.real = c1.real * c2.real - c1.imag * c2.imag;
    result.imag = c1.real * c2.imag + c1.imag * c2.real;
    return result;
}

void printComplex(Complex c) {
    printf("%.2f + %.2fi\n", c.real, c.imag);
}

int main() {
    Complex c1 = {3.0, 4.0};
    Complex c2 = {1.0, 2.0};

    Complex sum = add(c1, c2);
    Complex difference = subtract(c1, c2);
    Complex product = multiply(c1, c2);

    printf("Sum: ");
    printComplex(sum);
    printf("Difference: ");
    printComplex(difference);
    printf("Product: ");
    printComplex(product);

    return 0;
}

在上面的代碼中，定義了一個Complex結構體來表示復數，然后定義了三個函數來實現復數的加法、減法和乘法運算。在main函數中，創建了兩個復數c1和c2，并調用相應的函數來進行運算，并輸出結果。