AT&T 6300 Programmer's Manual page 435

Syntax
remark
Remarks
REM
Statement
Allows explanatory remarks to be inserted in a
program.
REM remark
represents a sequence of characters
REM statements are not executed but are
output exactly as entered when the program is
listed.
REM statements may be branched into from a
GOTO or GOSUB statement. Execution will
continue with the first executable statement
after the REM statement.
Remarks may be added to the end of a line by
preceding the remark with a single quotation
mark (') instead of REM. The single quotation
mark may also be t'ntered just after the line
number, like REM.
Note
Do not use remarks in a DATA statement,
because they would be considered legal data.
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