Editing Job Control Language (section)

===Comments===
JCL files can be long and complex, and the language is not easy to read. OS JCL allows programmers to include two types of explanatory comment:
*On the same line as a JCL statement. They can be extended by placing a continuation character (conventionally "<code>X</code>") in column 72, followed by "<code>// </code>" in columns 1–3 of the next line.
*Lines which contain only comment, often used to explain major points about the overall structure of the JCL rather than local details. Comment-only lines are also used to divide long, complex JCL files into sections.
<syntaxhighlight lang="jcl">
//MYJOB JOB ..........
//*  Lines containing only comments.
//******** Often used to divide JCL listing into sections ********
//STEP01 EXEC MYPROC             Comment 2 on same line as statement
//STEP02 EXEC PGM=.........      Comment 3 has been extended and       X
//         overflows into another line.
//INPUT01 DD DSN=STEP01.MYPR01.NEWFILE
</syntaxhighlight>