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     BRK(2)                                                     BRK(2)

     NAME
          brk, sbrk, break - change core allocation

     SYNOPSIS
          char *brk(addr)

          char *sbrk(incr)

     DESCRIPTION
          Brk 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 on the PDP11, 256 bytes on the
          Interdata 8/32, 512 bytes on the VAX-11/780).  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.

          In the alternate function 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(2), malloc(3), end(3)

     DIAGNOSTICS
          Zero is returned if the break could be set; -1 if the pro-
          gram requests more memory than the system limit or if too
          many segmentation registers would be required to implement
          the break.

     BUGS
          Setting the break in the range 0177701 to 0177777 (on the
          PDP11) is the same as setting it to zero.

     ASSEMBLER
          (break = 17.)
          sys break; addr

          Break performs the function of brk. The name of the routine
          differs from that in C for historical reasons.