@kbd{keyboard-characters}

Use the @kbd command for characters of input to be typed by users. For example, to refer to the characters M-a, write

@kbd{M-a}

and to refer to the characters M-x shell, write

@kbd{M-x shell}

The @kbd command has the same effect as @code in Info, but may produce a different font in a printed manual.

You can embed another @-command inside the braces of an @kbd command. Here, for example, is the way to describe a command that would be described more verbosely as "press an `r' and then press the RET key":

@kbd{r @key{RET}}  

This produces: r RET

You also use the @kbd command if you are spelling out the letters you type; for example:

To give the @code{logout} command, 
type the characters @kbd{l o g o u t @key{RET}}.

This produces:

To give the logout command, type the characters l o g o u t RET.

(Also, this example shows that you can add spaces for clarity. If you really want to mention a space character as one of the characters of input, write @key{SPC} for it.)