Files in This Directory
=======================

All files with the .tbl extension are braille tables which may be used with
BRLTTY. Note that BRLTTY has its own braille table format which may differ from
the format of braille table files used by other similar applications.

There are a few tools provided in this directory to manipulate the braille
tables. To build them, simply run `make'. The following tools will be made:

tbl2txt 	Uncompile a braille table file into an ASCII text file which 
	        can either be viewed with a regular text file browser or
                modified with a regular text editor and then compiled back into
                a braille table file (with txt2tbl).
txt2tbl		Compile a braille table file from an ASCII text file
		(as created by tbl2txt).
convtable	Convert a braille table file from one dot mapping to another.
ibm437toiso	Convert a braille table file from IBM's code page 437 format to 
		the ISO-8859-1 character set.
ibm850toiso	Convert a braille table file from IBM's code page 850 format to
		the ISO-8859-1 character set.


BRLTTY Braille Table Format
===========================

Each braille table is a binary file containing 256 bytes. The offset of each
byte is the value of its corresponding ASCII character which is to be
translated into braille dots, and the byte itself contains the braille dot
pattern for that character. The bits are assigned as follows:

	bit 0	bit 1		-->	dot 1	dot 4
	bit 2	bit 3		-->	dot 2	dot 5
	bit 4	bit 5		-->	dot 3	dot 6
	bit 6	bit 7		-->	dot 7	dot 8

This dot mapping was chosen because it makes programming prettier and more
efficient for things such as underlining, cursor support, and vertical braille
character shifting. A braille terminal which uses some other dot mapping
strategy (for example, a direct mapping of bits 01234567 to dots 12345678) must
translate BRLTTY's dot pattern into its own mapping within its own driver.
