How does the system differentiates between JCL comment statements (i.e., //* statements) and JES3 Statements (which also start with //* ) ?
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If the 4th column contains JES3 keyword, the line is considered to be JES3 statement, else it is
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System can't differentiates
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If the 3rd column contains JES3 keyword, the line is considered to be JES3 statement, else it is
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If the 1st column contains JES3 keyword, the line is considered to be JES3 statement, else it is
JES3 statements are identified by JES3 keywords appearing in column 4 of the line (after //*). If a JES3 keyword is found in this position, the line is treated as a JES3 control statement; otherwise, it is processed as a JCL comment.
Both JCL comment statements and JES3 control statements begin with the characters "//" in columns 1–3. The distinguishing rule is what comes immediately after: if a JES3 keyword starts right in column 4 (no blank separating it from the asterisk), the system treats the line as a JES3 control statement; if column 4 is blank (or doesn't contain a recognized JES3 keyword), it's treated as an ordinary comment. This lets JES3 parse its own directives while still allowing plain "// comment text" lines to pass through as documentation. The other options either claim the system can't tell the difference (false — it can, via this column rule) or point to the wrong column (1st or 3rd, which is occupied by "/" or "*", not where a keyword would start).