Create new files, whose name depends on a variable from the program

I'm trying to write a program that will save "X" number of simple textfiles- however, X is determined by the user once the program has run. I can't seem to find any help on the net as to how to solve the following two things, so any tips will be massively appreciated!

1) How do I declare these textfiles at the start of the program if I don't know how many there will be?

So far, I'm used to using:
```
FILE* outfile;
```

But what I really need is:

FILE* outfile_0, outfile_1, outfile_2... outfile_X;

The solution that comes to mind looks like a loop, but I know that this won't work!

for (i=0;I<X;i++){
    FILE* outfile_i     // obviously, this just literally calls it "outfile_i" 
}

2) How do I name them?

I want to call them simple names, such as "textfile_1, textfile_2" etc, but I don't see how that would be possible using:
```
outfile=fopen("C:\\textfile.txt","w");
```
Again, I thought perhaps making a loop (?!) but I know that this won't work:
```
for(i=0;i<X;i++){
    outfile_i=fopen("C:\\textfile_i.txt","w");
}
```

There's absolutely no way of knowing what variable "X" is before running the program.

EDIT: Problem solved- I wasn't aware you could create arrays of "FILE*", thanks for all the help!

Solution

You have to put all your FILE * variables in an array. I would do:

char filename[80];
char number[10];

/* Allocate our array */
FILE ** files = malloc((sizeof(FILE *) * X) + 1); /* We allocate a size of X+1 because we'll have X elements + a last NULL element. */

/* Populate our array */
for (int i = 0; i < X; i++)
{
    strcpy(filename,"C:\\textfile_");
    itoa(i, number, 10); /* Here 10 means we use decimal base to convert the integral value. */
    strcat(filename, number);
    strcat(filename, ".txt");

    files[i] = fopen(filename, "w");
}
files[i] = NULL; /* Here we set the last element of our array to NULL (so when we iterate over it we can stop when we encounter NULL). */

Then you can access all your files like this:

for (int i = 0; files[i] != NULL; i++)
{
    FILE * current = files[i];
    /* Do something with "current" here. */
}

PS: Some security checks are required:
malloc → Verify it doesn't return NULL.
itoa → Verify that output string is valid.
fopen → Verify that the file was opened.