Objective-C Programming: The Big Nerd Ranch Guide

12 The Heap

So far, your programs have used one kind of memory – frames on the stack. Recall that every function has a frame where its local variables are stored. This memory is automatically allocated when a function starts and automatically deallocated when the function ends. In fact, local variables are sometimes called automatic variables because of this convenient behavior.

Sometimes, however, you need to claim a contiguous chunk of memory yourself – a buffer. Programmers often use the word buffer to mean a long line of bytes of memory. The buffer comes from a region of memory known as the heap, which is separate from the stack.

On the heap, the buffer is independent of any function’s frame. Thus, it can be used across ...