One purpose of this site is to present a systematic, top-down description of the structure of braille as an aid to understanding for persons who learn better with a top-down approach, rather than with the more common bottom-up or detail-oriented approach. However, there are also lots of tips that would be useful for bottom-up learning.
The site is designed to be self-contained but does omit detail in areas that are well-covered by other sources; if you want to learn to read and write braille dots, this is a good place to start but, as clearly indicated, you will eventually need to go to other sources. The annotated links are a good starting point.
We hope that our unique summaries will demonstrate that there is more than one way to learn braille and will provide a useful guide to choosing the way that is likely to work best for you. All our pages are carefully cross-linked so you should be able to start wherever you choose.
Standard cells have one to six dots. The dot positions in a cell are arranged in two parallel columns of three positions each. The alphabet is composed of all 63 possible braille dot patterns that can be created from the different arrangements of one to six filled positions.
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In contrast to other alphabets, including the Roman alphabet, the cells have no conventional meanings. The meaning of a particular braille cell is determined by the particular braille code being used and usually also depends on local context. Further discussion of the context-sensitive meanings of braille cells is discussed in the section on braille codes and also in the page on DotlessBraille™.
A braille cell or sequence of braille cells that has a single meaning, such as two cells that create an uppercase letter, is generally called a braille symbol; the print character or sequence of characters that are transcribed by a braille symbol is called a sign. Although this useage is standard in braille, it is somewhat at odds with the terminology of semiotics and can be confusing to the novice.
A dot pattern is the arrangement of dots that make up a particular braille cell. The most widely-used method of specifying a dot pattern is to list the position numbers of the dots. The standard numbering system for dot positions numbers the positions for the left-hand column from 1-3 starting at the top of the column and from 4-6 for the right-hand column, again starting at the top of the column. For example, the cell with all six positions filled is called dot pattern 1-2-3-4-5-6. The ALT parameters displayed when hovering over the dots in the logo at the top of our main page use this standard system.Further discussion of methods for specifying dot patterns is discussed in the section on braille analogs.
What is a lower-cell dot pattern?
A lower-cell dot pattern is one in which all the filled dot positions are in the lower two-thirds of a cell; there are no dots at the top of either column. This designation is usually applied only to the ten dot patterns created by shifting the ten upper-cell dot patterns for the letters a-j and not to the other five dot patterns in the lower two-thirds of the cell.What is an upper-cell dot pattern?
A upper-cell dot pattern is one in which all the filled dot positions are in the upper two-thirds of a cell; there are no dots at the bottom of either column. This designation usually refers to the ten dot patterns for the letters a-j and not to the other five dot patterns in the upper two-thirds of a cell.What is an extended braille character set?
There are several types of extended braille characters sets. The most common one simply uses cells that have eight, rather than six, dots. A single eight-dot cell can be used to replace a standard two-cell symbol. For example, an upper case letter can be indicated by an extra dot in position 7 at the bottom of the left column, rather than being preceded by a separate capitalization indicator. Another type of extended braille character set, called DotsPlus, has either six or eight dots and includes other tactile symbols besides dots. (The eight-dot characters have only begun to gain in popularity with the use of refreshable braille displays. DotsPlus requires a special printer.)The three main codes used by Braille readers in the United States are the English literary code, the Nemeth code for mathematics and science, and the Music Code. Other codes used in the United States include the Computer Braille Code--a one-for-one transcription used for programming languages and literal expressions like web addresses--and specialized codes for sciences like chemistry. There are also codes based on the use of extended braille alphabets. This proliferation of codes has led to a call for a Unified Braille Code. The advantage would be that a braille reader would only have to learn one code; the difficulty is that a general code would be less efficient for any particular application than a specialized code. There are also many braille codes used for transcribing material printed in non-English languages--including languages that don't use the Roman alphabet.
The two most unique aspects of the literary and math codes are the use of embedded markup characters and of contractions.
Because of the limited number of cells in the standard braille alphabet, braille codes allow the cells to have multiple meanings. That is, they treat each dot pattern as a set of what I call semantic cells or s-cells. (A braille symbol can be either a single s-cell or a sequence of s-cells.) The meaning of a dot pattern depends on both the particular braille code in use and on local context. This is why braille equivalents that use one print character for one dot pattern aren't much help to people who don't know braille.
The context-sensitivity of braille is very different from that of print. Context often enriches the meaning of a print symbol and sometimes it takes several print characters to create a symbol: a single character intended to be subscript, for example, wouldn't be recognized as such in isolation. However, English text doesn't have the analogous situation to braille where the relative placement of a character can so completely determine semantics. For example, the dot pattern 2-5-6 has three meanings in literary braille: (1) at the start of a word it is the symbol for "dis", (2) in the middle of the word it is the symbol for "dd", and (3) following a word, it is the period punctuation mark. In the Nemeth code, it is also means the numeral four when it follows the Numeric Indicator which, of course, requires that Nemeth use a different dot pattern for the decimal point than a period. The basic way that DotlessBraille™ would simplify sighted understanding of braille is to use a different print representation for each unique meaning of each braille cell as used in a given code.
What is the literary braille code?
The literary or English braille code, sometimes called Braille 2 or contracted braille, is the most widely-used code in the United States for transcribing printed material using the standard, six-dot braille alphabet and is the one assumed here unless otherwise specified. (There is also an uncontracted form of English braille that is sometimes called Braille 1.)The literary code uses single cells as symbols for letters, part-words such as 'th' and 'ing', whole words such as 'and', punctuation marks, and indicators. Most of the single cells have additional context-dependent semantics including use as full-word and part-word contractions. The literary code also makes use of multiple-cell sequences for contractions.
What is the Nemeth braille code?
The Nemeth code, Figure. Nemeth numerals. |
Nemeth is essentially a superset of a slightly modified literary braille. The most notable modification to literary braille is for numerals, which use the corresponding lower-cell dot patterns rather than the upper-cell ones. Since the lower-cell dot patterns are the same as the punctuation marks, Nemeth requires the use of a Punctuation Indicator for changing back to that symbol set as well as a Numeric Indicator.
The Nemeth code is intended to reflect the appearance, presentation, or syntax of mathematics more than its semantics. This allows a braille transcriber to transcribe mathematical texts with little knowledge of the underlying mathematics. Further discussion of the relationship between this characteristic of the Nemeth code and transcribing issues is on the page on transcribing.
Lots of additional information about the Nemeth code has just (February 2002) been posted. Start here to learn more about Nemeth.
This page was last changed March 2, 2002.