This option supplies information about the ‘@’ control codes (see AT commands). It shows the associated style-file parameters that can be used to remap the codes (but don’t do that!), and it displays the precedence. (Some codes such as ‘@@’ may be used anywhere; others such as ‘@*’ begin a new section or part of section. Codes that begin the definition part are labelled by ‘[D]’; codes that begin the code part are labelled by ‘[C]’; codes that begin a new section are labelled by ‘[S]’.)
The option produces two columns of output: the first is sorted numerically, the second alphabetically. The notation ‘USED_BY_OTHER’ means that this command is ignored by whatever processor (FTANGLE or FWEAVE) is currently being run, but may be used by the other processor. (For technical reasons, a very few commands such as ‘@i’ do not show up in this output at present.)
If one says just ‘-@’, information about all control codes is produced. Selected control codes may be queried by listing them after the ‘-@’. For example, to learn about the commands ‘@~’ and ‘@a’, say ‘-@~a’. Remember to quote certain characters on UNIX systems—e.g., ‘-@'*?'’. If a command is used by neither processor, its description will be replaced by a question mark.