Hands-On System Programming with Linux

The program break

When a process or thread wants memory, it invokes one of the dynamic memory routines—usually malloc(3) or calloc(3); this memory (usually) comes from the heap segment. As mentioned earlier, the heap is a dynamic segment – it can grow (toward higher virtual addresses). Obviously though, at any given point in time, the heap has an endpoint or top beyond which memory cannot be taken. This endpoint—the last legally reference-able location on the heap – is called the program break.