This document provides an overview of the Unicode standard for character encoding. It discusses the design goals of being universal, consistent, and able to encode all written languages. Unicode represents characters as abstract code points from 0 to 10FFFF in hexadecimal and defines UTF-8, UTF-16, and UTF-32 encoding forms to represent these code points with 8, 16, or 32-bit units. The encoding forms allow lossless transformation between representations. UTF-8 is commonly used in XML documents while UTF-16 and UTF-32 are used by different operating systems.

1. Notes on a Standard:
UNICODE
Elena-Oana Tabaranu
elena.tabaranu@info.uaic.ro
UAIC, Iasi

2. Plan
● Introduction
● Design Goals
● Code Points and Characters
● Encoding Forms, UTF-32, UTF-16, UTF-8
● Conclusion
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3. Introduction
● UNIversal character enCODing system
● Unicode = universal character encoding scheme
for written characters and text
● Advantages
● Consistent way of encoding multilingual text
● Data stability instead of proliferating character sets
● Encode ALL characters used for the written languages (> 1
million characters can be encoded)
● Creates a foundation for global software
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4. Design Principles
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5. Characters, not Glyphs
● The Unicode Standard draws a distinction between
characters and glyphs.
● Characters are the abstract representations of the
smallest components of written language that have
semantic value.
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6. Logical Order
● The order in which
Unicode text is stored
in the memory
representation is
called logical order
● Unicode Standard
includes characters to
explicitly specify
changes in direction
when necessary
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7. Code Points and Characters
● Abstract characters are
encoded internally as
numbers
● Codespace: 0 to 10FFFF16
=> 1,114,112 code points
available
● Abstract character -> code
point
● Example:
U+0061 latin small letter a
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8. Encoding Forms
● Encoding forms specify how
each code point is to be
expressed as a sequence of
one or more code unit (8-bit,
16-bit, 32-bit units)
● Encoding forms for Unicode
characters: UTF-8, UTF-16,
UTF-32
● Each form can be efficiently
transformed into either of the
other two without any loss of
data
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9. UTF-32
● The simplest Unicode encoding form
● Each Unicode code point is represented directly
by a single 32-bit code unit (fixed-width)
● restricted to representation of code points in
the range 0..10FFFF16
● Example:
U+10000 is represented as <00010000>
● preferred encoding form for processing
characters on most Unix platforms 9

10. UTF-16
● Code unit values often change from the code
point value => conversion required
● Variable-width encoding:
➢ U+0000..U+FFFF are represented as a single 16-bit
code unit
➢ U+10000..U+10FFFF are represented as pairs of
16-bit code units (surrogate pairs)
● Optimized for BMP (Basic Multilingual Plain) =
majority of common-use characters for all
modern scripts of the world
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11. UTF-8
● UTF-8 encodes each character (code point) in 1 to 4
octets (8-bit bytes), with the single–octet encoding
used only for the 128 US-ASCII characters
● U+0000 to U+007F → 1 byte
● above → 2, 3, up to 4 bytes
● Backwards compatible with ASCII
● Standard for XML (XHTML) documents
● Example:
U+10000 is represented as <F0 90 80 80>
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12. Conclusion
● The Unicode Standard is a superset of all
characters in widespread use today.
● It contains characters from major international
and national standards (e.g. the SGML
standard) as well as prominient industry
character sets (e.g. industy code from Apple,
Adobe, Fujitsu, etc).
● Responds to changing industry demands by
encoding important new characters (e.g. the €
sign )
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13. Questions?
● Thank You!
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