7.1. Allocating Memory on the Heap

A process can allocate memory by increasing the size of the heap, a variable-size segment of contiguous virtual memory that begins just after the uninitialized data segment of a process and grows and shrinks as memory is allocated and freed (see Figure 6-1 in Section 6.4). The current limit of the heap is referred to as the program break.

To allocate memory, C programs normally use the malloc family of functions, which we describe shortly. However, we begin with a description of brk() and sbrk(), upon which the malloc functions are based.