|If N < 0||Set up file master as next phase and halt|
|If N = 0||Halt after completing one task|
Read dump locklet of user is n < 0
Call file master to carray out one task. On entry to file master
B83 = n ∨ J4 and B70 to 77 = w(ba) to w(ba+3.4)
Exit conditions as normal for file master but :-
If n = 1.0 on entry and B80 positive even on exit then B80 is the head pointer for a file that is deleted.
The response in B81 must be copied to the users Ba.
If n = m.1 J4 then this creates a B.S.D. from the file whose head pointer is m. The file master will read and write blocks in this file but will not attempt to extend it. If n is even and positive then n points to the 7-halfword title and contains 0.2 if the file is to be used in read only mode.
The system will also rely on the following extracodes being available for file manipulation in block mode : 1021, 1260, 1267, 1273, 1274
Reason for entry in B83 is as follows
|0.4||Create and open for writing|
|0.6||Create from pending stream|
|1.1||Delete file that is already opened|
|1.4||Open file for reading|
|2.5||Close file after reading|
|3.1||Close file after writing|
|2.0||Open block file for writing|
For the above entries the data in B70 to 77 is as follows:
|Entry||File Title/Status||Batch No.||MFD pointer||Head Pointer|
Success exit with m = Head Pointer after open for Reading. m ≠ 0 after other activities that succeed.
Operation permissible but locked out
m is reason ≥ 200
Requested operation is illegal and m is error number ≥ 100
File Master is broken and should be killed for fault m.
If Entry to file master was for reasons 0.4, 0.6, 1.4 or 2.0 then B81 = MFD pointer
If Entry to file master was from 1026 extracode call then B81 = response to be returned to user's Ba.
For other entries B81 is undefined.
The file master will be on-line to the consol in the Titan room. If BREAK is used on this then the file master should be freed with fault 65 set and not killed.
Extracode facilities for the following will also be used in the Mk.2 file master
Copyright © circa 1966 University of Cambridge Computer Laboratory. Distributed by permission. Thanks to Barry Landy, Roger Needham and David Hartley for giving permission to distribute these documents. Thanks to Barry Landy for lending me the paper document (handwritten) from which this was typed. Any typographical errors probably arose in the course of retyping.
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