Yodl's standard macro package supports the following macros to change fonts:
    itemization(
    it() tt(bf(text)): sets tt(text) in boldface.
    it() tt(em(text)): sets tt(text) emphasized, usually in italics.
    it() tt(tt(text)): sets tt(text) in teletype. 
    )
    Furthermore, the tt(tt()) macro does em(not) expand macros occurring
inside its argument. That means that you can safely write:
        verb(
    In Yodl, you can use tt(includefile(somefile)) to include a file
    in your document.
        )
    The tt(tt()) macro should not be used for long listings of verbatim text;
use tt(verb()) to set code samples etc..

    Yodl's standard macro package has no commands to change font sizes, as the
size is changed internally when appropriate (e.g., in section titles), nor is
there a default macro to define other font-families.

