He also had a device which looked rather like a large electronic calculator. This had about a hundred small buttons and a screen about four square inches big. It looked very complicated, and this was why it was printed “Don’t Panic” on the cover of it in large friendly letters. This device was in fact one of the most remarkable books that ever came out — The Hitchhiker’s Guide to the Galaxy. It was designed as an electronic book but not in the normal book form, because if printed on paper it will occupy several large buildings that are a bit inconvenient to carry around.
Beneath that in Ford Prefect’s bag were also a few pens, a notepad, and a bath towel from Marks and Spencer. The Hitchhiker’s Guide to the Galaxy has a few things to say on the subject of towels. A towel, it says, is about the most useful thing that a hitch hiker can have. Partly it has great practical value — you can wrap it around you for warmth when you find yourself alone on some foreign planet; you can lie on it on the brilliant sand of the beaches; you can sleep under it beneath the stars when the weather affords; use it to sail a mini raft down the river; wet it for use in hand-to-hand-combat; wrap it round your head to protect yourself from the smell of the swamps; you can wave your towel as an emergency signal, and of course dry yourself off with it if it still seems to be clean enough.
More importantly, a towel has immense psychological value. For some reason, if an ordinary person discovers that after travelling for a long time a hitch hiker still has his towel with him, he will automatically assume that he also has a toothbrush, matches, soap, tin of biscuits, flask, compass, map, gnat spray, raincoat, tent and so forth. Furthermore, he will then happily lend the hitch hiker any useful item that could have been lost in a journey. Because after all an ordinary person will always think that a man who travelled through the galaxy and still has his towel with him deserves some respect from the others.