Two processes with no common ancestor

• A

  An anonymous pipe is too small to carry the data two separate programs exchange, so a named pipe with its larger kernel buffer is required instead

• B

  An anonymous pipe is inherited through fork, so unrelated processes cannot reach it; a named pipe has a path both can open

• C

  Anonymous pipes are one-way and named pipes are two-way

• D

  Anonymous pipes are removed when the shell exits, so a named pipe persists