//JOBLIB and //STEPLIB are similar in that both specify one or more load libraries that contain programs that are not part of the system. As far as I know //JOBLIB has always been in OS/360 type systems. //STEPLIB appeared rather late in OS/360 (release 17, I think it was).
SYSPRINT is a DD name commonly used to specify a data set containing data that is suitable for printing on line oriented printers.
SYSOUT has multiple meanings.
- It is a keyword on a DD statement used to specify an output class, the name of a supplemental program used when the data set is actually printed, and the name of a form used when printing the data set. For better or worse some of this has been subverted for other purposes. One fairly popular output management product uses the SYSOUT program name to specify a report name within the output management system.
- It is a DD name used by some programs. Most sort programs use SYSOUT as their primary message data set.
- It is a noun used as a generic reference to data sets intended to be printed; "my program prints messages to SYSOUT," or "check SYSOUT."