    BREAK(II)                     8/5/73                    BREAK(II)

    NAME
         break, brk, sbrk - change core allocation

    SYNOPSIS
         (break = 17.)
         sys break; addr

         char *brk(addr)

         char *sbrk(incr)

    DESCRIPTION
         Break sets the system's idea of the lowest location not used
         by the program (called the break) to addr (rounded up to the
         next  multiple  of  64 bytes).  Locations not less than addr
         and below the stack pointer are not in the address space and
         will thus cause a memory violation if accessed.

         From  C,  brk  will set the break to addr.  The old break is
         returned.

         In the alternate entry sbrk, incr more bytes  are  added  to
         the  program's  data space and a pointer to the start of the
         new area is returned.

         When a program begins execution via exec the break is set at
         the highest location defined by the program and data storage
         areas.  Ordinarily, therefore, only  programs  with  growing
         data areas need to use break.

    SEE ALSO
         exec(II), alloc(III), end(III)

    DIAGNOSTICS
         The  c-bit  is  set if the program requests more memory than
         the system limit or if more than  8  segmentation  registers
         would be required to implement the break.  From C, -1 is re-
         turned for these errors.

    BUGS
         Setting the break in the range 0177700  to  0177777  is  the
         same as setting it to zero.

                                  - 1 -