#define FIRNUMBER 25
#define SIGNAL1F 1000
#define SIGNAL2F 4500
#define SAMPLEF  10000
#define PI 3.1415926

float InputWave();
float FIR();

float fHn[FIRNUMBER]={ 0.0,0.0,0.001,-0.002,-0.002,0.01,-0.009,
                       -0.018,0.049,-0.02,0.11,0.28,0.64,0.28,
                       -0.11,-0.02,0.049,-0.018,-0.009,0.01,
                       -0.002,-0.002,0.001,0.0,0.0
                     };
float fXn[FIRNUMBER]={ 0.0 };
float fInput,fOutput;
float fSignal1,fSignal2;
float fStepSignal1,fStepSignal2;
float f2PI;
int i;
float fIn[256],fOut[256];
int nIn,nOut;

main()
{
 nIn=0; nOut=0;
 f2PI=2*PI;
 fSignal1=0.0;
 fSignal2=PI*0.1;
 fStepSignal1=2*PI/30;
 fStepSignal2=2*PI*1.4;
 while ( 1 )
 {
  fInput=InputWave();
  fIn[nIn]=fInput;
  nIn++; nIn%=256;
  fOutput=FIR();
  fOut[nOut]=fOutput;
  nOut++;    /* break point */
  if ( nOut>=256 )
  {
   nOut=0;  
  }
 }
}

float InputWave()
{
 for ( i=FIRNUMBER-1;i>0;i-- )
  fXn[i]=fXn[i-1];
 fXn[0]=sin((double)fSignal1)+cos((double)fSignal2)/6.0;
 fSignal1+=fStepSignal1;
 if ( fSignal1>=f2PI ) fSignal1-=f2PI;
 fSignal2+=fStepSignal2;
 if ( fSignal2>=f2PI ) fSignal2-=f2PI;
 return(fXn[0]);
}

float FIR()
{
 float fSum;
 fSum=0;
 for ( i=0;i<FIRNUMBER;i++ )
 {
  fSum+=(fXn[i]*fHn[i]);
 }
 return(fSum);
}