16-02-2013, 11:12 AM
Unicode
Unicode[.ppt (Size: 278 KB / Downloads: 57)
Computers and Alphabets
Computers also have names for letters
The letter ‘a’ is called ‘61’ in one ‘language’
The letter ‘a’ is called ‘U+0061’ in another ‘language’
Why do computers use numbers for the names for letters?
Because they store all information in number form.
Technical detail: they store information as ‘bytes’; each ‘byte’ consists of 8 ‘bits’; each ‘bit’ is either the number ‘0’ or ‘1’’
Computer programs ‘translate’ the names into letters on the screen or in print
Result: you see a, a, a, a, a, a, etc. (different fonts, but the same letter)
ASCII versus Unicode
ASCII (American Standard Code for Information Exchange)
ASCII and Unicode are two computer ‘languages’ for naming letters
The ASCII name for ‘a’ is ‘61’
The Unicode name for ‘a’ is ‘U+0061’
ASCII
Computer systems can represent up to 256 letters
Technical detail: with one 8-bit byte (28 = 256)
Another technical detail: ASCII only uses 7 bits (27 = 128)
The first 32-127 are called ASCII letters (characters)
On all computers, the ASCII letters named 32-127 look the same.
E.g., ‘35’ looks like upper-case ‘A’ on all modern computers
Technical detail: why only up to 127? Excluding 0, that’s all you can represent with 27 combinations of bits)
Another technical detail: what happened to 1-32? That’s for control characters like the ‘option’ key.
ASCII Problem
While computers can represent 256 names for letters, no one agrees on what letters the numbers 128-256 stand for.
That’s why your Mac Cayuga font shows up as gibberish on a Windows computer.
The number ‘250’ doesn’t mean the same thing on a Mac as it does on a Windows PC.
Unicode: fixing the ASCII problem
Unicode aims to provide a unique name for every letter ever used…on the planet.
It has room for 1,000,000 names.
Everyone agrees on what letters the names stand for.
Technical details not discussed here: getting from names like ‘U+0061’ to the letter ‘a’ on your computer.
Unicode
Many letters have already been given an Unicode name.
Modern computers can display any letter that has a Unicode name.
Unicode and Cayuga
There’s no special character block for Cayuga
That’s because all the Cayuga characters can be made up from already existing Unicode characters
the Unicode Consortium won’t let you duplicate already existing characters.