The following conventions are used.
Literal input, names of keys, command names and command options, and system processes appear like this.
Names of files, directories, URLs, filesystems, and databases appear like this.
Names of devices and device types, user or system logins, groups, and aliases appear like this.
User-replaceable variables appear like this.
Other internal software elements, such as system calls, routines, primitives, kernel parameters, and environment variables, appear like this.
System messages and command-line prompts appear like this.
Code samples and file contents appear like this.
Menus, forms, graphical user interfaces, and their elements appear in the normal font.