It is an unknow line then.
The parameter of a line are separated by one or more whitespace.
In the case you mention "0//" this is the first parameter of the line, where a linetype 0 through 5 is expected. So it is an invalid line.
It's up to you as the author of the application what to do with that line![Smile Smile](https://forums.ldraw.org/images/smilies/smile.png)
Taken from: http://www.ldraw.org/article/218
The parameter of a line are separated by one or more whitespace.
In the case you mention "0//" this is the first parameter of the line, where a linetype 0 through 5 is expected. So it is an invalid line.
It's up to you as the author of the application what to do with that line
![Smile Smile](https://forums.ldraw.org/images/smilies/smile.png)
Code:
Basic parsing / file content
An LDraw file consists of one command per line. There is no line length restriction. Each command consists of optional leading whitespace followed by whitespace-delimited tokens. Some commands also have trailing arbitrary data which may itself include internal whitespace; such data is not tokenized, but treated as single unit according to the command.
Whitespace is defined as one or more spaces (#32), tabs (#9), or combination thereof.