IBM's job control language -- the shell of the mainframe.
Designed for easy processing from punch cards of the OS360 system.
Significant source of LegacyProblems.

The reference guide [1] and the user's guide [2] are on line available.

Quote of the year on page 25 of the user's guide, _Chez MVS_

--ArieVanDeursen && TobiasKuipers