Passing a double array from main to another function

Could someone give me an example of how to pass a double array from the main method/function to another function. I need to pass by reference. Meaning, what I update in the function called by main needs to be reflected in the original array in the main function. I have tried some stuff with passing by reference and using pointers, but I am having trouble.

I figured I could "cheat" around this problem by making my two dimensional array global, but my compiler gives me errors saying that I can't instantiate (may not be exact terminology) the array outside of a function.

I hope this is clear. Thanks in advance.

Yet another "My code produces errors" without any mention of either the actual code or the actual errors :(

Code:

---

void foo ( double x[10][20] ) {
  /* do stuff with x[row][col] */
}
int main ( ) {
  double x[10][20];
  foo( x );
}

---

Simply copy the declaration of the array you want to pass as a parameter to the function into the parameter declaration of that function.
Access the array inside foo() in exactly the same way as you would in main()

Thank you.