and grep will search through the first-named file to see if it contains the string "ndo" and put the results into the second-named file, which he can then check quite a bit later. He can also do "grep bun" and "grep dok" and if the results of all of these greps are true then he can be pretty confident that he has successfully coded the sequence " BUNDOK " into that one file. In the same way he can code " COORDINATES " into some other file and " LATITUDE " into another, and various numbers into others, and finally by using another command called "cat" he can slowly combine these one-word files into longer ones. All of these demands the same ridiculous patience as, say, tunneling out of a prison with a teaspoon, or sawing through iron bars with a nail file. But there comes a point, after he’s spent about a month in jail, when suddenly he’s able to make a window appear on the screen that contains the following message: