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Use the @code command to indicate text that is a piece of a program and which consists of entire syntactic tokens. Enclose the text in braces.

Thus, you should use @code for an expression in a program, for the name of a variable or function used in a program, or for a keyword. Also, you should use @code for the name of a program, such as diff, that is a name used in the machine. (You should write the name of a program in the ordinary text font if you regard it as a new English word, such as `Emacs' or `Bison'.)

Use @code for environment variables such as TEXINPUTS, and other variables.

Use @code for command names in command languages that resemble programming languages, such as Texinfo or the shell. For example, @code and @samp are produced by writing `@code{@@code}' and `@code{@@samp}' in the Texinfo source, respectively.

Note, however, that you should not use @code for shell options such as `-c' when such options stand alone. (Use @samp.) Also, an entire shell command often looks better if written using @samp rather than @code. In this case, the rule is to choose the more pleasing format.

It is incorrect to alter the case of a word inside an @code command when it appears at the beginning of a sentence. Most computer languages are case sensitive. In C, for example, Printf is different from the identifier printf, and most likely is a misspelling of it. Even in languages which are not case sensitive, it is confusing to a human reader to see identifiers spelled in different ways. Pick one spelling and always use that. If you do not want to start a sentence with a command written all in lower case, you should rearrange the sentence.

Do not use the @code command for a string of characters shorter than a syntactic token. If you are writing about `TEXINPU', which is just a part of the name for the TEXINPUTS environment variable, you should use @samp.

In particular, you should not use the @code command when writing about the characters used in a token; do not, for example, use @code when you are explaining what letters or printable symbols can be used in the names of functions. (Use @samp.) Also, you should not use @code to mark text that is considered input to programs unless the input is written in a language that is like a programming language. For example, you should not use @code for the keystroke commands of GNU Emacs (use @kbd instead) although you may use @code for the names of the Emacs Lisp functions that the keystroke commands invoke.

In the printed manual, @code causes TeX to typeset the argument in a typewriter face. In the Info file, it causes the Info formatting commands to use single quotation marks around the text.

For example,

Use @code{diff} to compare two files.

produces this in the printed manual:

Use diff to compare two files.

and this in the Info file:

Use `diff' to compare two files.

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