A Pascal string is a byte giving the length of the string, and this many bytes following which contain the string itself. A fixed-size Pascal string is the same, but followed by some undefined bytes to pad the whole thing to a fixed size:

   "Hello" as Pascal string:       05 48 65 6C 6C 6F
           with fixed length 10:   05 48 65 6C 6C 6F xx xx xx xx xx
           (xx = undefined values)

The description of the `.cc' files is the definition of these: this file is my personal reference for PCC.