Thread: multiple file handling

I am trying to write code that will open and modify multiple files with similar prefixes and different "numbers," ie, data001, data002 etc. I have written something that I thought would work, but it seems to be faulty, please help.

Code:

int main(void)
{
	//these are the variables. You need to put your data files in the folder where this is compiled
	
	//m->slope, x->velocity, y-> number of counts and sums. 
	//n->number of points in background
	double m, x, y;
	double leftend, rightend; /*these define the region where there is absorption*/
	int n=0, numpoints;
    FILE *in;  /* our file pointer */
               /* the file name (we'll change the number later) */
	FILE *newfold; /*the output file*/
    
	char *fname = "data000.txt";
	char *output = "folded000.fld";

               /* the digits as characters */
    char digit[10] = {'0','1','2','3','4','5','6','7','8','9'};
    int i;     /* this is our counter */
    int d1;    /* this is the hundreds digit */
    int d2;    /* this is the tens digit */
    int d3;    /* this is the ones digit */

	printf("At what velocity does the absorption begin? (mm/s): ");
	scanf("%lf", &leftend);
	printf("At what velocity does the absorption end? (mm/s): ");
	scanf("%lf", &rightend);

    for( i = 1; i <= 100; i++ ){
       d1 = i/100;             /* form file name */
       d2 = (i - 100*d1)/10;
       d3 = (i - 100*d1 - 10*d2);
	   printf("d1 = %d, d2 = %d, d3 = %d\n", d1, d2, d3);
       
	   
	   /*the program crashes after this step*/
	   fname[4] = digit[d1];   /* assume less than 999 files */

thanks in advance

Josh

Wow, thanks a lot itsme, that worked fine and is a lot more transparent than my method. Talk to you later.