Epson LX-80, Operating Manual

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Computer and printer interaction would be terribly confusing if
diff e r e nt kind s of computers and printers used different numbers for
th e sa m e l e tt e r of the alphabet . Therefore, most manufacturer s of
co mputer s, printers , and software use the American Standard C ode
fo r In f ormati o n Interchange, usually referred to as ASCII (pr o-
nounc e d ASK-Key) . The ASCII standard covers the decimal nu m-
b e r s from 0 t o 127 and includes codes for printable characters (l et-
t e r s, punctu a t i on , numerals , and mathematical symbols) and a f ew
co ntr o l c o d es , s uch as the codes for sounding the bell and perfor m-
i n g a carr i age r e turn.
A lth o u g h o th e r codes are not standardized in the computer indu s-
t ry, th e ASCII system means that at least the alphabet is st a nd ar-
d i ze d. A pr og rammer or engineer knows, for example , that 72 i s t h e
de cim a l c od e f or a capital Hand 115 is the code for a lower case s n o
mat te r wh a t s ystem he or she is using .
ESCape Codes
A lthou g h t h e original ASCII standard was designed to use th e de-
ci m a l numb ers 0 through 127 , computer and printer manufactu rers
soon exte nd ed this range (to 0 through 255) in order to make r oom
fo r m ore feat ures . On the LX-80 , for example , the codes from 160
t h ro u g h 254 a re used for italic characters. Because even this ex-
te nd e d i s n o t e nough for all the features used on modem print ers ,
th e r a n ge i s further extended with a special code called the Esc ape
co d e. Thi s co d e is often printed with the first three l e tters capitali zed
(E S Ca p e) o r a bbreviated as ESC or <ESC>.
Wh e n th e < ESC> code , which has the decimal value 27 , i s u sed,
p rint e r s a nd co mputers are not restricted to only 256 instructi ons.
T h e < ES C> code is a signal that the next code will be a pr i n ter
co ntrol cod e i nstead of text to print . For example , if the prin ter
rece iv es th e number 69 , it prints a capital E because 69 is the AS CII
co d e for th a t letter . If , however, the printer receives code 27 ju st
befo r e th e 6 9, it turns on emphasized mode, because <ESC> E is
th e code se qu e nce for emphasized.
Yo u can see how important the <ESC> code is by looking at
A pp e ndic es A , Band C . You will see that nearly every code t he
L X - 8 0 u ses i s an <ESC> code.