The most often used interfaces are:
Other dynamic memory allocation interfaces are memalign(3C), valloc(3C), and realloc(3C)
malloc returns a pointer to a block of memory at least as large as the amount of memory that is requested. The block is aligned to store any type of data.
free returns the memory that is obtained from malloc, calloc, realloc, memalign, or valloc to system memory. Trying to free a block that was not reserved by a dynamic memory allocation interface is an error that can cause a process to crash.
calloc returns a pointer to a block of memory that is initialized to zeros. Memory reserved by calloc can be returned to the system through either watchmalloc or free. The memory is allocated and aligned to contain an array of a specified number of elements of a specified size.
memalign allocates a specified number of bytes on a specified alignment boundary. The alignment boundary must be a power of 2.
valloc allocates a specified number of bytes that are aligned on a page boundary.
realloc changes the size of the memory block allocated to a process. realloc can be used to increase or reduce the size of an allocated block of memory. realloc is the only way to shrink a memory allocation without causing a problem. The location in memory of the reallocated block might be changed, but the contents up to the point of the allocation size change remain the same.