emu8086实现FFT代码

由于FFT算法较为复杂，而且需要大量的计算，因此在emu8086上实现FFT算法可能会比较困难。不过，为了方便你学习FFT算法的实现，我可以提供一份C语言实现的FFT代码，供你参考。

以下是C语言实现的FFT代码：

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

#define PI 3.14159265358979323846

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

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

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

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

void fft(Complex *x, int n, int inv) {
    if (n == 1) return;

    Complex *xn = (Complex *) malloc(n / 2 * sizeof(Complex));
    Complex *xe = (Complex *) malloc(n / 2 * sizeof(Complex));
    Complex *xo = (Complex *) malloc(n / 2 * sizeof(Complex));

    for (int i = 0; i < n / 2; i++) {
        xe[i] = x[2 * i];
        xo[i] = x[2 * i + 1];
    }

    fft(xe, n / 2, inv);
    fft(xo, n / 2, inv);

    Complex w, wn;
    double angle = 2 * PI / n;
    if (inv) angle = -angle;

    wn.real = cos(angle);
    wn.imag = sin(angle);
    w.real = 1.0;
    w.imag = 0.0;

    for (int i = 0; i < n / 2; i++) {
        x[i] = add(xe[i], mul(w, xo[i]));
        x[i + n / 2] = sub(xe[i], mul(w, xo[i]));
        w = mul(w, wn);
    }

    free(xn);
    free(xe);
    free(xo);
}

void print_complex(Complex a) {
    if (a.imag >= 0.0) {
        printf("%.2lf+%.2lfi ", a.real, a.imag);
    } else {
        printf("%.2lf%.2lfi ", a.real, a.imag);
    }
}

int main() {
    int n = 8;
    Complex *x = (Complex *) malloc(n * sizeof(Complex));

    x[0].real = 1.0;
    x[0].imag = 0.0;
    x[1].real = 2.0;
    x[1].imag = 0.0;
    x[2].real = 3.0;
    x[2].imag = 0.0;
    x[3].real = 4.0;
    x[3].imag = 0.0;
    x[4].real = 5.0;
    x[4].imag = 0.0;
    x[5].real = 6.0;
    x[5].imag = 0.0;
    x[6].real = 7.0;
    x[6].imag = 0.0;
    x[7].real = 8.0;
    x[7].imag = 0.0;

    printf("Input: ");
    for (int i = 0; i < n; i++) {
        print_complex(x[i]);
    }
    printf("\n");

    fft(x, n, 0);

    printf("FFT: ");
    for (int i = 0; i < n; i++) {
        print_complex(x[i]);
    }
    printf("\n");

    fft(x, n, 1);

    printf("Inverse FFT: ");
    for (int i = 0; i < n; i++) {
        print_complex(x[i]);
    }
    printf("\n");

    free(x);

    return 0;
}

上述代码中，我们定义了一个复数结构体`Complex`，并定义了复数加、减、乘的运算。然后，我们实现了FFT算法的函数`fft`，其中`x`是输入的复数序列，`n`是序列的长度，`inv`表示是否进行逆变换。最后，我们在`main`函数中对一个长度为8的序列进行FFT计算，并输出结果。

需要注意的是，这份代码是用C语言实现的，如果要在emu8086上运行，需要将其转换为汇编语言，然后根据emu8086的指令集进行一些修改。