There are also significant differences depending on who wrote the manuals. Back in the day, the MVT Supervisor PLM was excellent and the Utilities manual was dreadful. The quality of logic manuals took a nosedive when IBM went HIPO, and again when IBM adopted "task oriented documentations". Things seem to get better and worse in waves.
I've also seen some dreadful 3rd party documentation, e.g., discussing UNPK as though it could only operate on decimal data. -- Shmuel (Seymour J.) Metz http://mason.gmu.edu/~smetz3 ________________________________________ From: IBM Mainframe Assembler List [[email protected]] on behalf of Charles Mills [[email protected]] Sent: Saturday, January 30, 2021 2:23 PM To: [email protected] Subject: Re: TBEGINC question Not an MVS- or IBM-specific comment at all ... I have noticed over the years a difference in rigor between hardware and software documentation. I have attributed it to cultural differences in the two engineering mindsets, but I really don't know. Hardware documentation tends IMHO to be rigorous. The PoOp -- just as an example -- tells you exactly what will happen for many "stupid -- don't do that" cases, such as branching to an odd address. For reserved flag bits in an instruction it specifies whether they are ignored, cause a specification exception, or result in unpredictable outcomes. Software documentation tends to be much more "here is how to use the feature" leaving unspecified "what happens if you do something stupid?" The answer tends to be "don't do that" rather than "here is exactly what will happen." Charles -----Original Message----- From: IBM Mainframe Assembler List [mailto:[email protected]] On Behalf Of Peter Relson Sent: Saturday, January 30, 2021 7:29 AM To: [email protected] Subject: Re: TBEGINC question <snip> It appears that the editorial rules for Principles of Operation are stricter than those for Services. </snip> They certainly are. A lot stricter. Related to the fact that the machine has to enforce restrictions. Software does not "have to" (but of course it can be nice if it does).
