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Job control language (JCL) is a scripting language executed on an IBM mainframe operating system. It consists of control statements that designate a specific job for the operating system.
JCL provides a means of communication between the application program, operating system and system hardware.
JCL is considered to be one of the rude script languages run on IBM OS/360 batch systems. It can define data set names, parameters and system output devices. One common feature in both DOS and OS JCL is the unit of work, which is called a job. A job consists of several small steps for running a specific program and is identified by cards called job cards, which indicate the beginning of the job and define exactly how the job is to be executed.
Both DOS and OS operating systems use 71 characters per line. However, the maximum length is 80 characters. Characters 73-80 are used for locating the error areas reported by the OS.
When a JCL statement becomes too lengthy and exceeds the 71-character limit, it can be extended using a continuation card. A statement can be continued to as many cards as necessary by ending all the JCL cards excluding the last card at an instance where a comma is used, or by using (//) at the start of the continuation card in column one and using at least a one-space character.