Next time, please post your code between code tags.
Fuzzy pictures are useless for copy/pasting your work into a fixed up example.
So, briefly
Code:
#define N 100
int main ( ) {
struct something Re[N+1] = { 0 }; // your struct, initialised
for ( int i = 1 ; i <= N ; i++ ) {
char filename[100];
sprintf(filename,"S809_%d.dat",i);
FILE *fp = fopen(filename,"r");
// your while loop, adjusting Re1 to Re[i]
fclose(fp);
}
}
But watch out if your N * sizeof(struct something) is very large (like more than 1MB).
If N isn't a compile time constant, say so.