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By Root 1511 0

we make with our mouths to form words are a code intelligible to anyone who can hear our voices and understands the language that we speak. We call this code "the spoken word," or "speech." We have other code for words on paper (or on stone, on wood, or in the air, say, via skywriting). This code appears as handwritten characters or printed in newspapers, magazines, and books. We call it "the written word," or "text." In many languages, a strong correspondence exists between speech and text. In English, for example, letters and groups of letters correspond (more or less) to spoken sounds.

For people who can't hear or speak, another code has been devised to help in face-to-face communication. This is sign language, in which the hands and arms form movements and gestures that convey individual letters of words or whole words and concepts. For those who can't see, the written word can be replaced with Braille, which uses a system of raised dots that correspond to letters, groups of letters, and whole words. When spoken words must be transcribed into text very quickly, stenography or shorthand is useful.

We use a variety of different codes for communicating among ourselves because some codes are more convenient than others. For example, the code of the spoken word can't be stored on paper, so the code of the written word is used instead. Silently exchanging information across a distance in the dark isn't possible with speech or paper. Hence, Morse code is a convenient alternative. A code is useful if it serves a purpose that no other code can.

As we shall see, various types of codes are also used in computers to store and communicate numbers, sounds, music, pictures, and movies. Computers can't deal with human codes directly because computers can't duplicate the ways in which human beings use their eyes, ears, mouths, and fingers. Yet one of the recent trends in computer technology has been to enable our desktop personal computers to capture, store, manipulate, and render all types of information used in human communication, be it visual (text and pictures), aural (spoken words, sounds, and music), or a combination of both (animations and movies). All of these types of information require their own codes, just as speech requires one set of human organs (mouths and ears) while writing and reading require others (hands and eyes).

Even the table of Morse code shown on page 4 is itself a code of sorts. The table shows that each letter is represented by a series of dots and dashes. Yet we can't actually send dots and dashes. Instead, the dots and dashes correspond to blinks.

When sending Morse code with a flashlight, you turn the flashlight switch on and off very quickly (a fast blink) for a dot. You leave the flashlight turned on somewhat longer (a slower on-off blink) for a dash. To send an A, for example, you turn the flashlight on and off very quickly and then on and off at a lesser speed. You pause before sending the next character. By convention, the length of a dash should be about three times that of a dot. For example, if a dot is one second long, a dash is three seconds long. (In reality, Morse code is transmitted much faster than that.) The receiver sees the short blink and the long blink and knows it's an A.

Pauses between the dots and dashes of Morse code are crucial. When you send an A, for example, the flashlight should be off between the dot and the dash for a period of time equal to about one dot. (If the dot is one second long, the gap between dots and dashes is also a second.) Letters in the same word are separated by longer pauses equal to about the length of one dash (or three seconds if that's the length of a dash). For example, here's the Morse code for "hello," illustrating the pauses between the letters:

Words are separated by an off period of about two dashes (six seconds if a dash is three seconds long). Here's the code for "hi there":

The lengths of time that the flashlight remains on and off aren't fixed. They're all relative to the length of a dot, which depends on how fast the flashlight