[Tex/LaTex] ` (backtick) used for

tex-core

When redefining a category code of accessing a character in Plain-TeX style a backtick is present

\catcode`\"=\active
\char`\\

What is used for? Is it used in another situations?

Best Answer

backtick followed by a character or single-character command name is one of the tex syntaxes for a number. It is the character code of the character

\catcode`\"=\active
\catcode"22=\active
\catcode34=\active
\catcode'42=\active

are all the same thing with the number 34 being entered as the character code of ", in hex, in decimal and in octal.

This syntax can be used anywhere tex is looking for a number, not specifically for catcodes.

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