ASCII stands for American Standard Code for Information Interchange. It is the most common way of representing letters and numbers on a computer. Each character is represented by a number—for example, the letter A has the numeric value 65, and the letter a has the numeric value 97 (lowercase letters have a value that is 32 greater than their uppercase versions).

Values below 32 are called control codes—they were defined as nonprinting characters to control early computer terminal devices. The most common control codes for Arduino applications are listed in Table G-1.

Table G-2 shows the decimal and hexadecimal values of the printable ASCII characters.

Characters above 128 are non-English characters or special symbols and are displayed in the Serial Monitor using the UTF-8 standard (http://en.wikipedia.org/wiki/UTF-8). Table G-3 lists the UTF-8 extended character set.

You can view the entire character set in the Serial Monitor using this sketch:

/*
 * display characters from 1 to 255
 */

void setup()
{
  Serial.begin(9600);
  for(int i=1; i < 256; i++)
  {
     Serial.print(i, BYTE);
     Serial.print(", dec: ");
     Serial.print(i,DEC);
     Serial.print(", hex: ");
     Serial.println(i, HEX);
  }
}

void loop()
{
}

Note that some devices, such as LCD displays (see Chapter 11), may use different symbols for the characters above 128, so check the data sheet for your device to see the actual character supported.