Question

What is the difference between the free store and the heap?

Answer 1

Free store is a term that I associate more with the operating system, with the context in which programs are run. It's the sum of the available memory on the machine. It's a quite generic term.

The heap is a characteristic of a given process as it's running an executable. Usually, when the process is started up, it gets some amount of stack and another amount of heap space. Often the stack starts in the process' high memory and increases towards lower addresses. The heap starts from low memory and increases towards higher process addresses. This is a common way to allocate two partitions of changing resources, and it allows a simple check for overflow in either area: you just compare the heap's available-start-address to the process' top-of-stack pointer.