Determines the lowest virtual address that is not used with the
    program.

    Format

      #include  <stdlib.h>

      void *brk  (unsigned long int addr);

1 - Argument

 addr

    The lowest address, which the function rounds up to the next
    multiple of the page size. This rounded address is called the
    break address.

2 - Description

    An address that is greater than or equal to the break address
    and less than the stack pointer is considered to be outside the
    program's address space. Attempts to reference it will cause
    access violations.

    When a program is executed, the break address is set to the
    highest location defined by the program and data storage areas.
    Consequently, brk is needed only by programs that have growing
    data areas.

3 - Return Values

    n                  The new break address.
    (void *)(-1)       Indicates that the program is requesting too
                       much memory. errno and vaxc$errno are updated.

4 - Restriction

    Unlike other C library implementations, the Compaq C RTL memory
    allocation functions (such as malloc) do not rely on brk or
    sbrk to manage the program heap space. Consequently, on OpenVMS
    systems, calling brk or sbrk can interfere with memory allocation
    routines. The brk and sbrk functions are provided only for
    compatibility purposes.