User Guide

Editing Fonts
67
Characters, Codes and Glyphs
A font is a col le c t i o n o f g l y p h s t h a t u s u a l l y h a v e a c o m m o n d e s i g n . E a c h f o n t
h as a h e ad er th a t s t o r e s t o p - l e v e l i n f o r m a t i o n , s u c h a s t h e f o n t n a m e a n d
s tyle , in an or g anis ed wa y.
Character Mapping
Text in digital form is a collection of codes — integer numbers. When text
is entered into a computer we (with the help of a text processor program)
replace characters with codes. When text is printed or previewed on the
screen, the printing program performs the reverse process — replacing
codes with character shapes (glyphs) that it gets from the font.
Fon
t
Te xt
A character mapping standard is a set of rules that defines the relation
between characters and the codes that are used to represent these
characters in the computer. There are many mapping standards used in the
world to help use different languages. The main difference between
mapping standards is the size of the code. There are one-byte, double-byte
and multi-byte mapping standards. With a one-byte mapping standard
only 8 bits of information is used to represent each character, so it’s
possible to use only 256 characters.
A D ou bl e -b yte mapping sta nd ar d use s two b yte s (1 6 bits ) for e ver y ch a r a cter .
So it’s poss ibl e to ma p 6 55 36 ch ar ac ter s. Mu ltib yte ma pping sta nd ar ds u s e
from one to fou r bytes for ever y c ha r ac te r — e xpa nd ing the c ode s pa c e to
b il lions of cha ra cte rs .
O ne -b yte e nc oding s tanda r ds a re enou g h to r e pr es e nt mos t W es ter n
l ang ua ge s, bu t the y ru n out of r oom if mor e th a n one l angu a ge ne ed s to be
s upporte d, or in th e c as e of Ea s te rn la n g u a g e s t h a t u s e v e r y b i g a l p h a b e t s .
E ve n dou bl e-b yte enc od ing s ta nd a r d s c a n n o t c o v e r a l l t h e c h a r a c t e r s o f t h e
wor ld . The most wel l k nown and wid el y u se d dou bl e -b yte enc od ing s ta nda rd
is Unicode.