The debugger has extended the syntax of most languages to allow you to get the address of the first instruction that a source line generates. If you do not specify a file via the string, then the current file is used. If you specify a DOLLAR as the line-number, then the last line in the file that generated any instructions is used.
line-address
: ATSIGN string COLON line-number
| ATSIGN line-number
line-number
| DOLLAR