N point DFT or IDFT of sequence

N point DFT  or IDFT of  sequence

Problem Statement :Find the N point DFT / IDFT of the given sequence x (n) .Plot the magnitude spectrum|X(K)| Vs K. (Analyze the output for different N and the same input sequence x(n). Also observe the periodicity and symmetry property) .

1:  #include<stdio.h>  
2:  #include<conio.h>  
3:  #include<complex.h>  
4:  void main()  
5:  {  
6:     float x[20],pi=22.0/7.0;  
7:     complex X[20];  
8:     int k,n,N;  
9:     clrscr();  
10:     printf("\t\t\tDFT Fourier Transform\n");  
11:     printf("\nEnter the number samples in the sequence x(n), N = ");  
12:     scanf("%d",&N);  
13:     printf("\nEnter the samples of sequence x(n)\n");  
14:     for(n = 0; n < N; n++)  
15:     {  
16:       printf("x(%d) = ",n);  
17:       scanf("%f",&x[n]);  
18:     }  
19:     for(k = 0; k < N; k++)  
20:     {  
21:       X[k]=complex(0.0,0.0);  
22:       for(n = 0; n < N; n++)  
23:       {  
24:        complex temp=complex(0.0,-2*pi*k*n/N);  
25:        X[k] = X[k] + x[n]*exp(temp);  
26:       }  
27:     }  
28:     printf("\nThe %d point DFT of given sequence is...",N);  
29:     printf("\n\tReal X(k)\t\tImaginary X(k)");  
30:     for(k = 0; k < N; k++)  
31:      printf("\nX(%d) = %3.6f\t\t %3.4f",k,real(X[k]),imag(X[k]));  
32:     getch();  
33:  }