FWIW yes, I go back to A little bit of CP/67 and OS/360 on a 360/67 in 1967 Hardcore DOS/360 on 360/40s and /50s starting in 1968 (My first paid software job.) Hardcore OS/360 starting around 1972 or so. No SVC 99!
And I disagree. Variables and file handles are not the same as DD names at all. I can hard-code a z/OS program to copy 'MYFILE1' to 'MYFILE2'. It can then copy any dataset to any other dataset (with many limitations, but you get the idea). There is no directly equivalent function in Windows or Linux. I cannot code arbitrary internal names (in variables or otherwise) and then map them to real external names at run time. (AFAIK -- correct me if I am wrong. Yes, stdin and stdout come close.) Charles -----Original Message----- From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf Of Seymour J Metz Sent: Friday, January 7, 2022 9:52 AM To: [email protected] Subject: Re: ... Re: Top 8 Reasons for using Python instead of REXX for z/OS I would say that what substitues for ddnames is variables and file handles. You go back to OS/360? -- Shmuel (Seymour J.) Metz http://mason.gmu.edu/~smetz3 ________________________________________ From: IBM Mainframe Discussion List [[email protected]] on behalf of Charles Mills [[email protected]] Sent: Friday, January 7, 2022 10:16 AM To: [email protected] Subject: Re: ... Re: Top 8 Reasons for using Python instead of REXX for z/OS A file handle is basically a DCB, or rather, a pointer to a DCB. The thing it points to is a black box, so there are no compatibility issues comparable to the 24-bit addresses in DCBs. What "substitutes" for DD name indirection in many or most non-mainframe systems is that "dynamic allocation" is standard. I remember the days before SVC 99. It was something of a hack job to write a program that decided on a dataset name during execution. OTOH for most non-mainframe operating systems the standard way to specify a file at open time is by external file name. If you are going to prompt the user for a file name during execution (as most interactive programs do) then file name indirection would be counterproductive. Charles -----Original Message----- From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf Of Bob Bridges Sent: Friday, January 7, 2022 6:47 AM To: [email protected] Subject: Re: ... Re: Top 8 Reasons for using Python instead of REXX for z/OS Took me an embarrassingly long time to notice that what I thought was silly in some of the non-mainframe programming languages I'd encountered, the feature called a "file handle", allowed programs in those languages the same flexibility that DD names give in JCL. --- Bob Bridges, [email protected], cell 336 382-7313 /* Democracy is the recurrent suspicion that more than half of the people are right more than half of the time. -E B White */ -----Original Message----- From: IBM Mainframe Discussion List <[email protected]> On Behalf Of Tom Brennan Sent: Friday, January 7, 2022 00:13 Maybe a bigger issue is with non-mainframe folks wondering why JCL is there in the first place. I started with microcomputers, programming things in BASIC where we were told to hard-code full filenames in the program itself. Already I could see how silly that would be in production, having to change the source code just to work with different files. Unix solved that in clever ways with parameter passing, stdin, and things like that which work well in shell scripts. Mainframes solved it with 8 character DD names and JCL redirection. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
