Sbrk Ibrk request additional working memory char *sbrk int increase char *ibrk int increase Sbrk requests an allocation from free memory and returns a pointer to its base. "Sbrk()" requests the system to allocate "new" memory from outside the initial allocation. Users should read the Memory Management section of this manual for a fuller explanation of the arrangement. Ibrk requests memory from inside the initial memory allocation. Sbrk and ibrk return -1 if the requested amount of contiguous memory is unavailable.