Program and global variable storage

Using Arduino Programming Questions
1

Apologies in advance for such a basic question... why does this global array "x" not consume any global variable (or program) storage?

char x[20000];

void setup() {
  // put your setup code here, to run once:
}

void loop() {
  // put your main code here, to run repeatedly:
}

After compilation:

Sketch uses 6944 bytes (2%) of program storage space. Maximum is 262144 bytes.
Global variables use 3044 bytes (4%) of dynamic memory, leaving 62492 bytes for local variables. Maximum is 65536 bytes.

2

Because you haven't used it for anything. The compiler optimizes the code, if anything is not used, it doesn't allocate memory or code space for it.

3

Ah, thanks, adding

x[0] = 'a';

inside the loop forced the allocation:

Global variables use 23044 bytes...

4

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