> On 6 Nov 2013, at 11:32 pm, Paul Gilmartin <[email protected]> wrote:
>
>> On Wed, 6 Nov 2013 22:45:01 +0800, David Crayford wrote:
>>
>> JCL is neither simple or powerful. It's a piece of poorly designed junk that
>> should never have made GA. Even it's original implementers admit that it's
>> rubbish. Try explaining the reverse logic of condition codes to a youngster
>> and they will die laughing.
>>
>> Hey, how do I do a loop in this code?
>>
>> Forget it kid, they didn't have rewind on punch card readers.
> With all due respect (even I can muster all the respect due to JCL),
> the declarative character, as opposed to procedural, of JCL provides
> a couple advantages:
>
> o It's possible to determine at initiation (some of) the resources
> needed by a job and assure that they will be available, thereby
> avoiding (some) deadlocks. (When we had our first couple
> systems and no GRS, linkage editor reserve deadlocks were a
> recurrent problem.)
>
> o Auditors can tell by inspection who's doing what to whom. Thei
> like that.
>
> It would be impossible to do either in a Turing-complete command
> language.
>
I'm not so sure about that. CL has declare commands which does the same thing.
And it's Turing complete.
> The "reverse logic of condition codes" probably was intuitive to an
> assembler or FORTRAN programmer who thought of branching
> around a statement.
>
> DOS, like TSO, places the data set allocations before the command
> ("phase"?), which seems more natural than the JCL convention.
> After all, which do you do first? Oops. I forgot: JCL is declarative
> rather than procedural.
>
> JCL met the needs of the 360 well. This is a different century.
>
> -- gil
>
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