How are two-dimensional arrays formatted in memory?
- by Chris Cooper
In C, I know I can dynamically allocate a two-dimensional array on the heap using the following code:
int** someNumbers = malloc(arrayRows*sizeof(int*));
for (i = 0; i < arrayRows; i++) {
someNumbers[i] = malloc(arrayColumns*sizeof(int));
}
Clearly, this actually creates a one-dimensional array of pointers to a bunch of separate one-dimensional arrays of integers, and "The System" can figure you what I mean when I ask for:
someNumbers[4][2];
But when I statically declare a 2D array, as in the following line...:
int someNumbers[ARRAY_ROWS][ARRAY_COLUMNS];
...does a similar structure get created on the stack, or is it of another form completely? (i.e. is it a 1D array of pointers? If not, what is it, and how do references to it get figured out?)
Also, when I said, "The System," what is actually responsible for figuring that out? The kernel? Or does the C compiler sort it out while compiling?
