#include<stdio.h>
#include<math.h>
#include<float.h>
#include<malloc.h>
#include<stdlib.h>
void initial(int num_data, float* real, float* inm);
void enter_data(int num_data, float* data);
void wave_sin(int num_data, float* data);
void wave_cos(int num_data, float* data);
void decay(int num_data, float* data);
void random(int num_data, float* data);
void table(int num_data, char flag,
float* tablesin, float* tablecos);
void DFT(int num_data, char flag, float* real, float* img,
float* tablesin, float* tablecos);
float period;

void main()
{
int num_data;
int i;
char flag;
float *real, *img;
float *tablecos, *tablesin;
printf("PLEASE INPUT SAMPLE PERIOD(Second):");
scanf("%f", &period);
printf("PLEASE INPUT SAMPLE POINT NUMBER:");
scanf("%d", &num_data);
fflush(stdin);
printf("DFT OR IDFT (D/I):");
flag=getchar();
if(flag==‘d’) flag=‘D’;
if(flag==‘i’) flag=‘I’;
printf("\n");
real=(float*)malloc(sizeof(float)* num_data);
img=(float*)malloc(sizeof(float)* num_data);
tablesin=(float*)malloc(sizeof(float)* num_data);
tablecos=(float*)malloc(sizeof(float)* num_data);
initial(num_data, real, img);
table(num_data, flag, tablesin, tablecos);
DFT(num_data, flag, real, img, tablesin, tablecos);
for(i=0; i<num_data; i++)
printf("%8d real=%12.6f img=%12.6f\n",
i, real, img);
free(real);
free(img);
free(tablesin);
free(tablecos);
}

void initial(int num_data, float* real, float* img)
{
int n;
for(n=0; n<num_data; n++)
{
real[n]=0;
img[n]=0;
}
printf("INITIAL REAL DATA\n");
enter_data(num_data, real);
printf("\nINITIAL IMG DATA\n");
enter_data(num_data, img);
}

void enter_data(int num_data, float* data)
{
int selection;
printf("FUNCTION SELECTION\n");
printf("1-----AMPLITUDE*SIN(2*3.1415926
*FREQUENCY*PERIOD*T)\n");
printf(&

quot;2-----AMPLITUDE*COS(2*3.1415926
*FREQUENCY*PERIOD*T)\n");
printf("3-----AMPLITUDE*EXP(-PERIOD)\n");
printf("4-----DATA=0\n");
printf("5-----ENTER DATA\n");
printf("ENTER SELECTION---");
scanf("%d", &selection);
switch(selection)
{
case 1:wave_sin(num_data, data);break;
case 2:wave_cos(num_data, data);break;
case 3:decay(num_data, data);break;
case 4:break;
case 5:random(num_data, data);break;
}
}

void wave_sin(int num_data, float* data)
{
float amplitude, frequency, c;
int n;
printf("PLEASE INPUT AMPLITUDE OF WAVE:\n");
scanf("%f", &amplitude);
printf("PLEASE INPUT FREQUENCY OF WAVE(Hz):\n");
scanf("%f", &frequency);
for(n=0; n<num_data; n++)
{
c=2*3.1415926*frequency*period*n;
data[n]=(float)(amplitude*sin(c));
}
}

void wave_cos(int num_data, float* data)
{
float amplitude, frequency, c;
int n;
printf("PLEASE INPUT AMPLITUDE OF WAVE:\n");
scanf("%f", &amplitude);
printf("PLEASE INPUT FREQUENCY OF WAVE(Hz):\n");
scanf("%f", &frequency);
for(n=0; n<num_data; n++)
{
c=2*3.1415926*frequency*period*n;
data[n]=(float)(amplitude*cos(c));
}
}

void decay(int num_data, float* data)
{
float amplitude, c;
int n;
printf("PLEASE INPUT AMPLITUDE OF WAVE\n");
scanf("%f", &amplitude);
for(n=0; n<num_data; n++)
{
c=-period*n;
data[n]=(float)(amplitude*exp(c));
}
}

void random(int num_data, float* data)
{
int n;
for(n=0; n<num_data; n++)
{
printf("PLEASE INPUT DATA[%d]:", n);
scanf("%f", &data[n]);
}
}

void table(int num_data, char flag,
float* tablesin, float* tablecos)
{
float w, c;
int n;
w=(float)(8*atan(1)/num_data);
if(flag==‘D’) w=-w;
for(n=0; n<num_data; n++)
{

c=w*n;
tablecos[n]=(float)cos(c);
tablesin[n]=(float)sin(c);
}
}

void DFT(int num_data, char flag, float* img,
float* tablesin, float* tablecos)
{
int i, j, L;
float *result_r, *result_i;
result_r=(float*)malloc(sizeof(float)*num_data);
result_i=(float*)malloc(sizeof(float)*num_data);
for(i=0; i<num_data; i++)
{
result_r=0;
result_i=0;
for(j=0; j<num_data; j++)
{
L=i*j%num_data;
result_r=result_r+real[j]*tablecos[L]
+img[j]*tablesin[L];
result_i=result_i+img[j]*tablecos[L]
-real[j]*tablesin[L];
}
}
if(flag==‘D’)
{
for(i=0; i<num_data; i++)
{
real=result_r;
img=result_i;
}
}
else if(flag==‘I’)
{
for(i=0; i<num_data; i++)
{
real=result_r/num_data;
img=result_i/num_data;
}
}
free(result_r);
free(result_i);
}