Special Characters

Certain characters have special meaning in L^ATEX. Typing these characters doesn't make them appear in the output. For example, the character % is used to add comments to L^ATEX input files: A % and everything that follows it on the line is ignored by L^ATEX.

The most important special character is the backslash, \. The backslash is used to give special commands to L^ATEX. For example, the L^ATEX logo itself is actually produced by the command \LaTeX. A command consists of a backslash followed by a sequence of letters. Also, a command can consist of a backslash followed by a single non-letter character. For example, if you want the special character % to appear in the output, you can type it as \%. \% is a command that tells L^ATEX to put a % into the output.

Other special characters include $, #, &, _, {, and }. These can be types at \$, \#, \&, \_, \{, and \}. The dollar sign is particularly important in L^ATEX: It is used to enclose mathematics. For example, the mathematical inequality $x<y$ is typed as $x<y$. This is called math mode. There are three special characters that only come out correctly in math mode: $<$, $>$, and $\vert$. These characters can be typed between dollar signs. For example: $<$. The backslash itself can be generated using the command \backslash in math mode; that is, $\backslash$ yields  $\backslash$ in the output. There are two more special characters, ~ and ^, that we will get to later.¹

Some characters that appear in documents can't be typed at all. An example is the left double quote mark, ``. In L^ATEX, this symbol is inserted into the output by typing two single left quotes: ``. You can type a right quote as two right single quotes, '' (although in fact typing the usual double quote character will give the same thing). Similarly, there are actually three types of dashes: the hyphen (-), the n-dash (-) that is used in number ranges such as 2003-2004, and the m-dash (--) that is used to separate text--like this--from the rest of the sentence. In L^ATEX, you type -, -, and -- as -, --, and ---.

There are many more special characters, especially when you consider mathematical symbols. These are entered into L^ATEX output using special commands. For example, the command \copyright gives ©, and \dag gives . There are a lot of commands that are valid only in math mode, and we will see some of these later. The command \dots gives the three dots that are usually used to represent an ellipsis; you need this because typing three periods gives ... and that doesn't look as good as ...

And finally, there are characters that are accented or otherwise decorated, such as the ö in coöperate. The most common accents are input as single-character commands in front of the letter that is to be accented. Type \'e, \`e, \"u, \~n, \^o, and \=a, for é, è, ü, ñ, ô, and a.