While using the Bloodshed Dev-C++ Compiler, Compiling the following program, I'm getting 31 errors, all in standard headers...
The program computes the DCT of a 16x16 pixel input of all 1's...

#include <math.h>
#include <fstream.h>
#define pi 3.14159

unsigned long int N = 16; //The size of the block the DCT is performed on
int Pixel[16][16];
long int DCTmatrix[16][16];

float Cosines(int x, int pixelnum)
{
float y = (2*x+1)*pixelnum*pi/(2*N);
return y;
}
void DCT()
{
unsigned long int j;
unsigned long int i;
unsigned long int x;
unsigned long int y;
long int temprounded;
float temp;
for (i = 0; i < N; i++)
{
for (j = 0; j < N; j++)
{
temp = 0;
for (x = 0; x < N; x++)
{
for (y = 0; y < N; y++)
{
temp = temp+Cosines(x, i)* Cosines(y, j)*Pixel[x][y];
}
}
}
temp = temp * sqrt (2 * N);
temprounded = temp;
DCTmatrix[i][j] = temprounded;
}
}

int main()
{
int counter;
int counter2;
for (counter = 0; counter < 16; counter++)
{
for (counter2 = 0; counter2 < 16; counter2++)
{
Pixel[counter][counter2] = 0;
}
}
DCT();
ofstream a_file("DCT.txt");
for (counter = 0; counter < 16; counter++)
{
for (counter2 = 0; counter2 < 16; counter2++)
{
a_file<<DCTmatrix[counter][counter2];
}
}
system("PAUSE");
return 0;
}

I'm a bit rusty on C/C++, but my suggestion is that the fstream is implemented differently on many compilers - maybe this is causing problems. Try using the fopen, fwrite and fclose instead:

#include <math.h>
#include <stdio.h>
//#include <fstream.h>
#define pi 3.14159

unsigned long int N = 16; //The size of the block the DCT is performed on
int Pixel[16][16];
long int DCTmatrix[16][16];

float Cosines(int x, int pixelnum)
{
float y = (2*x+1)*pixelnum*pi/(2*N);
return y;
}
void DCT()
{
unsigned long int j;
unsigned long int i;
unsigned long int x;
unsigned long int y;
long int temprounded;
float temp;
for (i = 0; i < N; i++)
{
for (j = 0; j < N; j++)
{
temp = 0;
for (x = 0; x < N; x++)
{
for (y = 0; y < N; y++)
{
temp = temp+Cosines(x, i)* Cosines(y, j)*Pixel[x][y];
}
}
}
temp = temp * sqrt (2 * N);
temprounded = temp;
DCTmatrix[i][j] = temprounded;
}
}

int main()
{
int counter;
int counter2;
for (counter = 0; counter < 16; counter++)
{
for (counter2 = 0; counter2 < 16; counter2++)
{
Pixel[counter][counter2] = 0;
}
}
DCT();
FILE *fp = fopen("DCT.txt", "w");
//ofstream a_file("DCT.txt");
for (counter = 0; counter < 16; counter++)
{
for (counter2 = 0; counter2 < 16; counter2++)
{
fwrite(&(DCTmatrix[counter][counter2]), 1, 1, fp);
//a_file<<DCTmatrix[counter][counter2];
}
}
fclose(fp);
//system("PAUSE");
return 0;
}

What line does the first error point at?

First Line:

31 c:\dev-c_~1\include\g__~1\iostream.h
from C:\DEV-C_~1\INCLUDE\G__~1\fstream.h:30,

Second Line:

6 c:/windows/desktop/dct.c
C:\DEV-C_~1\INCLUDE\G__~1\streambuf.h:35: parse error before string constant

I solved it... I don't know how, but I solved it.

I first switched the compilation type from C++ to C.

Then I switched it back to C++.

Maybe the compiler was accidentaly trying to compile it as a C program and not a C++ program...

Well, another problem...

Now the program outputs nonsense...

eg... A matrix that doesn't correspond to the input...

I'll try and work it out, I suppose.