Code_ The Hidden Language of Computer Hardware and Software - Charles Petzold [4]
At first, the definition of Morse code—and by definition I mean the correspondence of various sequences of dots and dashes to the letters of the alphabet—appears as random as the layout of a typewriter. On closer inspection, however, this is not entirely so. The simpler and shorter codes are assigned to the more frequently used letters of the alphabet, such as E and T. Scrabble players and Wheel of Fortune fans might notice this right away. The less common letters, such as Q and Z (which get you 10 points in Scrabble), have longer codes.
Almost everyone knows a little Morse code. Three dots, three dashes, and three dots represent SOS, the international distress signal. SOS isn't an abbreviation for anything—it's simply an easy-to-remember Morse code sequence. During the Second World War, the British Broadcasting Corporation prefaced some radio broadcasts with the beginning of Beethoven's Fifth Symphony—BAH, BAH, BAH, BAHMMMMM—which Ludwig didn't know at the time he composed the music is the Morse code V, for Victory.
One drawback of Morse code is that it makes no differentiation between uppercase and lowercase letters. But in addition to representing letters, Morse code also includes codes for numbers by using a series of five dots and dashes:
These codes, at least, are a little more orderly than the letter codes. Most punctuation marks use five, six, or seven dots and dashes:
Additional codes are defined for accented letters of some European languages and as shorthand sequences for special purposes. The SOS code is one such shorthand sequence: It's supposed to be sent continuously with only a one-dot pause between the three letters.
You'll find that it's much easier for you and your friend to send Morse code if you have a flashlight made specifically for this purpose. In addition to the normal on-off slider switch, these flashlights also include a pushbutton switch that you simply press and release to turn the flashlight on and off. With some practice, you might be able to achieve a sending and receiving speed of 5 or 10 words per minute—still much slower than speech (which is somewhere in the 100-words-per-minute range), but surely adequate.
When finally you and your best friend memorize Morse code (for that's the only way you can become proficient at sending and receiving it), you can also use it vocally as a substitute for normal speech. For maximum speed, you pronounce a dot as dih (or dit for the last dot of a letter) and a dash as dah. In the same way that Morse code reduces written language to dots and dashes, the spoken version of the code reduces speech to just two vowel sounds.
The key word here is two. Two types of blinks, two vowel sounds, two different anything, really, can with suitable combinations convey all types of information.
Chapter 2. Codes and Combinations
Morse code was invented by Samuel Finley Breese Morse (1791–1872), whom we shall meet more properly later in this book. The invention of Morse code goes hand in hand with the invention of the telegraph, which we'll also examine in more detail. Just as Morse code provides a good introduction to the nature of codes, the telegraph provides a good introduction to the hardware of the computer.
Most people find Morse code easier to send than to receive. Even if you don't have Morse code memorized, you can simply use this table, conveniently arranged in alphabetical order:
Receiving Morse code and translating it back into words is considerably harder and more time consuming than sending because you must work backward to figure out the letter that corresponds to a particular coded sequence of dots and dashes. For example, if you receive a dash-dot-dash-dash, you have to scan through the table letter