Besides the previously described macro tt(USECHARTABLE()), Yodl has one other
mechanism of activating and deactivating character translation tables. This
mechanism uses a stack, and hence, the related macros are appropriately named
tt(PUSHCHARTABLE()) and tt(POPCHARTABLE()).

startit()

    it() tt(PUSHCHARTABLE(name)) em(pushes) the currently active translation
    table onto a stack, and activates the table identified by tt(name). The
    argument may be emtpy; in that case, the zero-translation table is
    activated (analogously to tt(USECHARTABLE())).

    it() tt(POPCHARTABLE()) activates the translation table that was last
    pushed. There is no argument to this macro.

endit()

Using the push/pop mechanism is handy when a table must be temporarily
activated, but when it is not known which table exacty is active prior to the
temporary activation. E.g., imagine that you need to use a character table
called tt(listing) to typeset a listing, but that you do not know the current
table. The pushing and popping mechanism is then used as follows:

verb(\
COMMENT(First, we save the current table on the stack and
        we activate our "listing" table.)
PUSHCHARTABLE(listing)

COMMENT(Now the text is question is typeset.)
...

COMMENT(The previously active table is re-activated, whatever its name.)
POPCHARTABLE())
