Let's see if I can say anything related to DOS without BC_Programmer correcting me
A tilde is inserted into the filename by the Windows command prompt when the original filename was longer than 8 characters or contained spaces. The name 'My Documents' becomes 'MYDOCU~1'. If there was also a 'My DocuZZZZ' folder, it would be called 'MYDOCU~2' and so on. The name 'Keen 1' becomes 'KEEN1~1'.
