What is variable

hierarchical data structure.
Stack memory will never become fragmented whereas Heap memory can become fragmented as blocks of memory are first allocated and then freed.
Stack accesses local variables only while Heap allows you to access variables globally.
Stack variables can’t be resized whereas Heap variables can be resized.
Stack memory is allocated in a contiguous block whereas Heap memory is allocated in any random order.
Stack doesn’t require to de-allocate variables whereas in Heap de-allocation is needed.
Stack allocation and deallocation are done by compiler instructions whereas Heap allocation and deallocation is done by the programmer.