Debug assertion problem

Hi , I am new in this field.
I am trying to read float values from matlab file and trying to store it in buffer of size 1024 and then passing to my fft module .
But it shows some Debug assertion problem at last.
However values are written correctly in the buffer.
plz tell me the debug assertion problem.
Here is my code

Code:

 int main()
{
    FILE *fp;
    FILE *fp1;
	float line;
	float buffer[N];
	int nwritten;
	int i=0;
	fp1=fopen("result.txt","w");
   
	fp=fopen("decimalnewdata.txt","r");      //reading transmitted baseband data from a file
	if(fp==NULL)
	{
		puts("cannot open file");
		exit(1);
	}

while(!feof(fp)) /*here's my problem*/
{
fscanf(fp,"%f\n", &line); /*fscanf is used, reads data from file ignoring other ascii characters*/
printf("%f\n",line); /*just for checking*/
buffer[i]=line;
nwritten = fprintf(fp1,"%f\n", buffer[i]);
i=i+1;
}
printf("%d\n",i); 
   fclose(fp); 
   
   fclose(fp1);
  getch();
  return(0);
 }

Some reading to start with