How are disc and track number tags stored?

[AMJF]

This is a curious thing I've noticed since using these tags extensively, and it seems that different players handle these tags in different ways.

I thought they were simple integers, but then Mp3tag seems to store them as a count/total. How is that done? Can't be as simple as a string with a slash, surely?

[DetlevD]

This is a curious thing I've noticed since using these tags extensively, and it seems that different players handle these tags in different ways.
I thought they were simple integers, but then Mp3tag seems to store them as a count/total. How is that done? Can't be as simple as a string with a slash, surely?

Regarding the filetype MP3 read there ...
http://id3.org/id3v2.3.0#Declared_ID3v2_frames

... Mp3tag tag-field "Track" ...

TRCK
The 'Track number/Position in set' frame is a numeric string containing the order number of the audio-file on its original recording. This may be extended with a "/" character and a numeric string containing the total numer of tracks/elements on the original recording. E.g. "4/9".

... Mp3tag tag-field "DISCNUMBER" ...

TPOS
The 'Part of a set' frame is a numeric string that describes which part of a set the audio came from. This frame is used if the source described in the "TALB" frame is divided into several mediums, e.g. a double CD. The value may be extended with a "/" character and a numeric string containing the total number of parts in the set. E.g. "1/2".

DD.20140522.1215.CEST