Line numbers are not necessary and will be assigned.
Labels can consist of A-Z, a-z, 0-9, _, and -. They can be any length, but a maximum line length is 256 characters. Label “definitions” must start a line and end with a single colon. Labels can be referenced any place a line number can be used, currently: THEN, ELSE, [ON]GOTO, [ON]GOSUB, and ON ERROR.
Comments are any line that start with REM or // (C/C++ style single line comment notation). XB also has a “trailing comment” designated by a ! that causes the rest of the line to be ignored. The C-style // comments will be stripped from the code, but the REM and ! comments will be retained in the output.
Leading space is ignored so you can indent as much as you like.
Long lines can be split by ending a line with .. (double period). These lines will be joined into one long line and the XB limit of 140 characters will be checked.
The starting line number and line number increment can be specified.