ASCII
codes for Braille cells (Computer Braille codes)
Computerized Braille
printing is a reality, thanks to the advances made in Braille Embossing
machines. Braille Embossers are similar to the printers attached to a computer.
They are used for producing Braille documents directly from text typed
into a computer using Word Processors, Text Editors or similar applications.
Often a special utility is used to get the cells embossed since the Embossers
do not exactly behave like normal printers. The purpose of the utility
is to ensure that the correct Braille cells are embossed.
The point to remember
in this connection is that a Braille cell is a representation of not just
the letters of the alphabet but combinations of letters as well, including
all the punctuation marks. With only 63 cells, we observed that some cells
will have to be interpreted based on the context, e.g., cells representing
punctuation marks, also represent double letter combinations. A consequence
of this is that one cannot send ASCII codes of the text to be embossed
directly to the Embosser but map the text to appropriate cells and send
codes to the Embosser consistent with the cells to be embossed.
Take for example the
sentence "There are 63 Braille cells which have been grouped in to
7 categories, each category referred to as a line". When this text is represented
in Braille, rules of contractions may also be applied resulting in fewer
characters in the sentence. Now, there is no representation for a numeral
in Braille. Hence 63 or 7 or even the comma in the sentence cannot be sent
directly to the Embosser in the same manner as in regular printing because,
the codes sent to a normal printer support 96 different letters or symbols
while the codes sent to an Embosser can only indicate one of 63 cells.
This issue is handled
satisfactorily by defining a different set of ASCII codes to represent
the Braille cells. This set has only 63 codes which can be displayed as
cells and the computer has to send to the Embosser only these codes. The
purpose of the utility will now become clear because the utility will convert
the text in the document to be embossed into the embossing codes and send
the same to the Embosser. The term ASCII Braille now appears meaningful.
ASCII Braille refers to the mapping of the 63 Braille cells to ASCII codes
conforming to the specifications for embossing.
The table below gives
the mapping. The ASCII code for a cell is shown through the character indicated
below each cell. The codes are in increasing order starting with 32 for
the blank cell, 33 for the exclamation mark and ending with 95 for the
underscore character. ASCII values actually go upto 126 for normal Roman
letters. However, this braille cell mapping stops with 95. The codes from
96 to 122 may also be sent to Embossers but they merely repeat the cells
A-Z since Braille does not distinguish between upper case and lower case
consonants and vowels.
It is observed
that while the mapping has retained the standard ASCII codes for the letters
of the alphabet, the embossing codes corresponding to special symbols or
punctuation will emboss cells that will represent something different.
For example, the exclamation mark (code 33 decimal) sent to an Embosser
will print the cell (dots 2346) which represents the three letter combination
"the". To get the exclamation mark printed in Braille, one has to send
the ASCII code 54 (the numeral 6).
Knowledge of ASCII
Braille is required only for those who develop computer applications that
will transcribe text from different applications (such as word processors,
text editors etc.) into Braille.
Braille
Fonts
The mapping used in ASCII Braille is followed in creating Braille Fonts
which are useful for proof reading the output to be sent to the Embosser.
Software for Braille Transcription invariably use the Braille Fonts for
on-line verification. A Free Braille Fonts is available from the Royal
National Institute for the Blind in the U.K. The font is known as RNIB
font and works well for applications running under Microsoft Windows. This
font has been used in creating the picture shown above. The rectangle around
each cell is not part of the cell and has been introduced (at IIT Madras)
for improved readability.
