It is possible to display binary files or data, but the characters that are not drawable are viewed as a reverse question mark (191). This question mark is displayed only when the Xlib function XTextWidth returns 0 for the character. Unfortunately this is implementation dependent and in some cases, a simple blank character is viewed.
The Ctrl-q command (quoted char) allows you to insert
a non drawable character. For instance to insert a ^
L (new
page), just type Ctrl-q Ctrl-l.