After having read carefully P G Scott's document and having compared DDOS11C vs DDOS12A,
this is the situation:

- Fault 1 is already corrected on both files
- Fault 2 is already corrected on both files
- Fault 3 is already corrected on both files
- Fault 4 is already corrected on both files
- Fault 5 is ONLY corrected in DDOS12A	(filename validation exits to Basic)
- Fault 6 is ONLY corrected in DDOS12A	(Basic routines instead of ml for PROTECT and RENAME)
- Fault 7 is already corrected on both files
- Fault 8 is ONLY corrected in DDOS12A  (only 5 files open)
- Fault 9 is only corrected in DDOS12A  (CLOSE closes all files)
					(patch A OK, patch B in a different way that the one proposed by P G Scott, but functional too)
- Fault 10 is already corrected on both files

Concerning "Problems" only number 3 is corrected in DDOS11C
- Problem 1 - to avoid negative answers in some functions) 	- corrected in DDOS12A
- Problem 2 - INPUT closes files				- patch A) corrected in DDOS12A
								  patch B) MUST be removed from DDOS12A, prevents KILL to work properly
								  copy code from DDOS11C: CFEF to D000
- Problem 3 - SAVE could create non killable files		- is already corrected on both files
- Problem 4 - killed files ...					- partially corrected on DDOS12A
								  line 3 of the patch has not been applied:
								  		Patch		DDOS11C-12A
								  +179D (3)	20 DD 12	26 25 39
- Problem 5 - restore drives to track 0				- not corrected in any file


There is a non documented difference between the two files:
It is related to the PROTECT function and adds CLOSE file at the end of the command
	     DOS11C		     DOS12A
D795	26 E7	BNE $D77E	20 E5	BRA $D77C
D797	39	RTS		12	NOP

It seems that we can work with the unmodified DDOS11C as long as Faults 5,6,8 and 9 don't affect our work (same for Problems 1,2,4)

To work confidently with DDOS12A we should:
- remove patch B of Problem 2
- decide if line 3 of patch for Problem 4 is mandatory and if so apply it
	it adds a 'clear IRQ' before exiting the function. Is this mandatory?
	Surprisingly I have found it applied to the DDOS12dir but is not in DDOS12 nor DDOS12A
	So, I would apply this part too!
- evaluate the benefits of applying the patch for Problem 5 
	this could be a trial version
	
