Contents page Index (83KB) JCL JCL: /J-C-L/ n. 1. IBM's supremely rude Job Control Language. JCL is the script language used to control the execution of programs in IBM's batch systems. JCL has a very fascist syntax, and some versions will, for example, barf if two spaces appear where it expects one. Most programmers confronted with JCL simply copy a working file (or card deck), changing the ...