Developer | Burroughs / Unisys |
---|---|
Written in | ESPOL, NEWP |
OS family | Not Applicable |
Working state | Current |
Source model | Source available |
Initial release | 1961; 59 years ago |
Latest release | 19.0[1] / June 2019 |
Platforms | Burroughs large systems including the Unisys Clearpath/MCP |
Default user interface | Text user interface |
License | Proprietary |
Official website | MCP site |
GETSPACE
and FORGETSPACE
are the two main procedures handling memory allocation and deallocation. Memory needs to be allocated at process initiation and whenever a block is entered that uses arrays, files, etc. GETSPACE
and FORGETSPACE
not only handle memory space, they also allocate or deallocate the disk space where non memory resident data may be overlaid. Memory may be SAVE (i.e., memory resident), OVERLAYABLE (i.e., virtual memory) or STICKY (meaning memory resident, but movable). They are called upon e.g. by HARDWAREINTERRUPT
when a process addresses an uninitialized array or by FILEOPEN
.HARDWAREINTERRUPT
handles hardware interrupts and may call upon GETSPACE
, IO_FINISH
or the like.BLOCKEXIT
is called upon by a task exiting a block. BLOCKEXIT may in turn call FILECLOSE
, FORGETSPACE
or the like while cleaning up and releasing resources declared and used within that block.GEORGE
is the procedure that decides which process is the next one to receive CPU resources and is thus one of the few processes that uses the MoveStack instruction.