DB<5> printf "%04b", $mode ;
1000000111101101
  DB<6> printf "%04b",  07777;
111111111111
  DB<7>

##</code><code>##

  1000000111101101 &
  0000111111111111
  ================
= 0000000111101101

##</code><code>##

  DB<8> $c = $mode & 07777;

  DB<9> printf "%04b", $c;
111101101
  DB<10>

##</code><code>##

  DB<10> printf "%04o", $c;
0755
  DB<11>