程式碼示例：

float ar[1024],ai[1024];/* 原始資料實部，虛部 */

float a[2050];

void fft(int nn) /* nn資料長度 */

{

int n1,n2,i,j,k,l,m,s,l1;

float t1,t2,x,y;

float w1,w2,u1,u2,z;

float fsin[10]={0.000000,1.000000,0.707107,0.3826834,0.1950903,0.09801713,0.04906767,0.02454123,0.01227154,0.00613588,};

float fcos[10]={-1.000000,0.000000,0.7071068,0.9238796,0.9807853,0.99518472,0.99879545,0.9996988,0.9999247,0.9999812,};

switch(nn)

{

case 1024: s=10; break;

case 512: s=9; break;

case 256: s=8; break;

}

n1=nn/2; n2=nn-1;

j=1;

for(i=1;i<=nn;i++)

{

baia[2*i]=ar[i-1];

a[2*i+1]=ai[i-1];

}

for(l=1;l<n2;l++)

{

if(l<j)

{

t1=a[2*j];

t2=a[2*j+1];

a[2*j]=a[2*l];

a[2*j+1]=a[2*l+1];

a[2*l]=t1;

a[2*l+1]=t2;

}

k=n1;

while (k<j)

{

j=j-k;

k=k/2;

}

j=j+k;

}

for(i=1;i<=s;i++)

{

u1=1;

u2=0;

m=(1<<i);

k=m>>1;

w1=fcos[i-1];

w2=-fsin[i-1];

for(j=1;j<=k;j++)

{

for(l=j;l<nn;l=l+m)

{

l1=l+k;

t1=a[2*l1]*u1-a[2*l1+1]*u2;

t2=a[2*l1]*u2+a[2*l1+1]*u1;

a[2*l1]=a[2*l]-t1;

a[2*l1+1]=a[2*l+1]-t2;

a[2*l]=a[2*l]+t1;

a[2*l+1]=a[2*l+1]+t2;

}

z=u1*w1-u2*w2;

u2=u1*w2+u2*w1;

u1=z;

}

}

for(i=1;i<=nn/2;i++)

{

ar[i]=4*a[2*i+2]/nn; /* 實部 */

ai[i]=-4*a[2*i+3]/nn; /* 虛部 */

a[i]=4*sqrt(ar[i]*ar[i]+ai[i]*ai[i]); /* 幅值 */

}

}