Yes it was. On early Unix systems, each entry in a directory was bascially: struct dir { char name[14]; int inode; }; Adding a NUL b

Yes it was. On early Unix systems, each entry in a directory was bascially: struct dir { char name[14]; int inode; }; Adding a NUL byte might waste a full byte that could otherwise be used---remember, back when C was first developed, 10M disks were large and very expensive.