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Computer and printer interaction would be terribly confusing if
different kinds of computers and printers used different numbers for
the same letter of the alphabet. Therefore, most manufacturers of
computers, printers, and software use the American Standard Code
for Information Interchange, usually referred to as ASCII (pro-
nounced ASK-Key). The ASCII standard covers the decimal num-
(letters, punctuation, numerals, and mathematical symbols) and a few
control codes, such as the codes for sounding the beeper and per-
forming a carriage return.
Although other codes are not standardized in the computer indus-
try, the ASCII system means that at least the alphabet is standardized.
A programmer or engineer knows, for example, that 72 is the decimal
code for a capital H and 115 is the code for a lowercase s no matter
what system he or she is using.
ESCape Code
Although the original ASCII standard was designed to use the
decimal numbers 0 through 127, computer and printer manufacturers
soon extended this range (to 0 through 255) in order to make room
for more features. On the LX-80, for example, the codes from 160
through 254 are used for italic characters. Because even this extended
range is not enough for all the features used on modern printers, the
range is further extended with a special code called the Escape code.
This code is often printed with the first three letters capitalized
(Escape) or abbreviated as ESC or <ESC>.
With the ESCape code, for which decimal 27 is used, printers and
computers are not restricted to only 256 instructions. The ESCape
code is a signal that the next code will be a printer control code
instead of text to print. For example, if the printer receives the num-
ber 69, it prints a capital E because 69 is the ASCII code for that letter.
If, however, the printer receives a 27 just before the 69, it turns on
emphasized mode, because ESCape "E" is the code for emphasized.
You can see how important the ESCape code is by looking at
Appendix B. There you will see that nearly every code the LX-80
uses is an ESCape code.
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127 and includes codes for printable characters
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