Mitsubishi Electric MELSEC Q Series Programming Manual page 104

Precautions on using labels
• In a function, the same name as the function cannot be used for a label.
• A space cannot be used.
• A numeral cannot be used at the beginning of label name.
• A label name is not case-sensitive. An error may occur at compilation when the same label names with different cases
(example: 'AAA' and 'aaa') are declared.
• An underscore (_) cannot be used at the beginning or end of label name. Consecutive underscores (_) cannot be used for
data name and label name.
• For Simple projects, function names and function block names in common instructions and application functions can be
used.
• In structured ladder/FBD and ST programs, the same label name can be used for a global label and a local label by setting
the following option in GX Works2.
Check the "Use the same label name in global label and local label" item under [Tool]  [Options]  "Compile"  "Basic
Setting".
APPX
102
Appendix 2 Character Strings That Cannot Be Used in Label Names and Data Names