Mac OS similarly, over time, grew various short Pascal string types to be used i...

Mac OS similarly, over time, grew various short Pascal string types to be used in its APIs. https://opensource.apple.com/source/CarbonHeaders/CarbonHead...:

    typedef unsigned char Str255[256];
    typedef unsigned char Str63[64];
    typedef unsigned char Str32[33];
    typedef unsigned char Str31[32];
    typedef unsigned char Str27[28];
    typedef unsigned char Str15[16];

The 2^n-1 sizes are cache-line don’t need explanation, I think. 27 was the maximum length of a volume name in MFS, the original Macintosh file system (which was a strange mix of backwards (no directories) and forwards (255 character file names) thinking).

Str32 was used in AppleTalk (and probably a design error or bug; Str31 is a more ‘natural’ type)