Unicode: The Underlying Technology

All computer programs identify characters by number. International standards
correlate every number to a unique character, so that a computer file from
Europe, for example, can be properly typeset in Asia. It took decades before
a single standard international numbering system was established: Unicode.
Both TrueType and OpenType fonts use Unicode numbers to identify their
constituent characters.

The goal of Unicode is to assign a unique id number to every character,
linguistic symbol, or ideogram in all of the world’s languages, living or dead.
The number of such ids now exceeds 100,000.
To facilitate backward compatibility, and to support legacy documents,
today’s computing systems still suffer from vestiges of earlier numbering
systems. The first of these was ascii (the American Standard for Computer
Information Interchange), which used the numbers 0 through 127, as shown
in Figure 4.4. The original desktop computing systems—including Microsoft
dos and Windows and the Apple Macintosh os—used one-byte numbering
systems that were consistent through the ascii range but differed in the id
numbers assigned to the other 128 characters a font could contain. This made
communications between the two platforms needlessly complicated, with
characters often incorrectly displayed on a nonnative system.

For technical reasons, the id numbers assigned by Unicode are written in
hexadecimal format. Hexadecimal, in addition to using the numerals 0 through
9 to express numbers, also uses the letters A through F. This allows 16 values
to be expressed with a single character, like so: 0, 1, 2, 3, 4, 5, 6, 7, 8,
9, A, B, C, D, E, F. The letters following 9 represent 10, 11, 12, 13, 14, and
15, respectively, in our everyday counting system. In hexadecimal, the value
expressed as 0010 (Unicode values are always expressed using four “digits”) is
the equivalent of 16 in our normal base-10 system.

Fortunately, you don’t need to know anything more than this about hexadecimal
notation, and even the preceding paragraph is added only to explain


Post By Computer Zoom Design