Array length & allocation question

[Robert Atkinson]

Quick question concerning Array lengths and memory allocations.

When an array.length = array.length + 1 (or length - 1) happens, does the system
only increase (decrease) the memory allocation by 1 [unit] or does it internally
mantain a buffer and try to minimise the resizing of the array?

I think I can remember seeing posts saying to maintain the buffer yourself and
other posts saying it was done automatically behind the scenes.