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





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







NAME

     break - set program break



SYNOPSIS

     (break = 17.)

     sys break; addr



     char *sbrk(incr)



DESCRIPTION

     Break sets the system's idea of the lowest location not used

     by  the  program 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, the calling sequence is different; 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)



DIAGNOSTICS

     The c-bit is set if the program requests  more  memory  than

     the  system  limit  (currently 20K words), or if more than 8

     segmentation registers would be required  to  implement  the

     break.  From C, -1 is returned for these errors.
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