Each line sets properties for the newsgroup named in the first field. The name is immediately followed by a character that indicates whether the owning user is currently subscribed to the group or not; a colon indicates subscription, and an exclamation mark indicates nonsubscription. The remainder of the line is a sequence of comma-separated article numbers or ranges of article numbers, indicating which articles the user has seen.

Non-Unix programmers might have automatically tried to design a fast binary format in which each newsgroup status was described by either a long but fixed-length binary record, or a sequence of self-describing binary packets with internal length fields. The main point of such a binary representation would be to express ranges with binary data in paired word-length fields, in order to avoid the overhead of parsing all the range expressions at startup.

Such a layout could be read and written faster than a textual format, but it would have other problems. A nave implementation in fixed-length records would have placed artificial length limits on newsgroup names and (more seriously) on the maximum number of ranges of seen-article numbers. A more sophisticated binary-packet format would avoid the length limits, but could not be edited with the user's eyeballs and fingers — a capability that can be quite useful when you want to reset just some of the read bits in an individual newsgroup. Also, it would not necessarily be portable to different machine types.