TransAct Ithaca 280, Руководство программиста

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Unicode iTherm
®
280 Programmer’s Guide
Page 258 Rev K
About Unicode
Unicode is a way of mapping all characters and symbols in use by modern languages. A
Unicode character consists of two bytes. These two bytes, 16 bits, allows us to represent
more than 65,000 characters.
Most legacy computing devices use one byte to represent a character or symbol. This
single byte design causes a problem when we want to use Unicode to represent
characters. Some steps have been taken to accommodate this two byte character
representation. One, is the creation of a new operating system using a New Technology.
This new technology uses 16 bit data values to represent textual data. This new
technology works well to manipulate data on a computer, but legacy communication
technology only transmits data via a byte (8 bits) at a time.
MBCS (Multiple Byte Character Set) to the rescue, sometimes referred to as DBCS
(Double Byte Character Set). This is a way of encoding the Unicode data so that an
electronic device that uses bytes will not get confused when working with a Unicode
character.
Memory
A full Unicode font would have more than 50,000 characters. If each character was 16-
dots wide and-16 dots tall, each character would require 32 bytes of memory. 32 x
50,000 = 1,600,000 bytes to store all the characters‘ images. This is a very conservative
estimate, in reality, many characters take 32 dots wide and 32 dots high to represent the
image of the character. A 32-dot by 32-dot character image uses 128 bytes of memory.
128 x 50,000 = 6,400,000 bytes of memory to store all the characters.
Even though memory is much cheaper than in the past, 6.4MB is too big.
TransAct’s implementation of Unicode in the
iTherm
®
280.
Since each
printer is likely not to need all the characters of all languages, we don‘t need
to store all the 50,000+ characters. Also, many applications will desire a custom font
style (i.e. Fixed pitch, Arial, Script…).
To address both these criteria (custom font style and sub set of Unicode characters), We
have implemented a way to download any kind of font to the iTherm
®
280. Different sizes
and styles are supported, as well as fixed and variable pitch. The only real limit is the
amount of memory the printer has.
TransAct has created a font download utility program that runs on Windows 2000 and
Windows XP. This utility is available upon request. You must agree to use this utility with
fonts that you have the right to download to a printer. Contact your salesperson for more
information.