[gmokki]

SMS in Europe was max 140 bytes and they had various custom 7bit encodings for most western languages. SMS also supported ucs-2 aka Unicode with fixed 16bit codepoints which cannot do modern emojis, but all normal languages can be shown, whether your phone has/had the fonts was another matter.

And when concatenating the SMS messages the UserDatHhader had to be added taking minimum 6 bytes, thus reducing the bytes available from 140 to 134 bytes, which allows only 153 or 67 characters for each 7bit or unicode SMS messages respectively.