They developed a code in which certain combinations of smoke rising had special meaning. For example, two parallel columns of smoke indicated the successful return of a war party.
Almost anything that makes a noise has been used for signaling. Cyrus, an ancient Persdrums.
In modern times, people have communicated by letter, telegraph, and telephone. But no one method has become as widespread as quickly as the use of email. The first email message took place in 1971, and according to its sender, Ray Tomlinson, it was probably the following : "QWERTYUIOP." What was significant about that ?