Some comments on fdial.opl
--------------------------

For more details, see the accompanying file WLD.DOC.
Evidently, WLD.DOC is in a rather rough form, but you may still find
some of its contents useful.  NB I do not personally believe all of
the contents of WLD.DOC, but don't presently have the time to sort
the untruth from the truth.

The main steps in fdial.opl are:
    IOOPEN(h%,"WLD:",-1)
    IOW(h%,11,#adno%,fr%())
    while 1
        IOW(h%,23,cdata%(),#0)
        IOW(h%,13,fr%(),#0)
    endwh

The IOW(... 11 ...) is a WR_FIND_COUNTRY to put the i/o channel to
WLD: into "finding country mode", in which the effect of any
subsequent WR_NEXT or WR_BACK is to nudge by country.  (The default
is by city.)  Since the search string is null (this is the #adno%),
the very first country in the database is found.

The IOW(... 23 ...) is a WR_GET_COUNTRY_DATA to get a WR_COUNTRY_DATA
struct into cdata%().  There is no second parameter to this function
so the final #0 is merely to prevent the translator whinging.

The IOW(... 13 ...) is a WR_NEXT, to nudge to the next country in the
database.

The result of a WR_NEXT (or a WR_FIND_COUNTRY) is a WR_FIND_RES
struct, which (see WLD.DOC) is 42 bytes long (ie 21 Opl integers). 
The line of opl
    adco%=addr(fr%()+21)
positions the variable adco% to the beginning of where the country
name part of this struct will be written.  The (rather laborious)
routine GETZTS: is used to extract a C-style ZTS (zero terminated
string).  (I would certainly re-write GETZTS: using OSs or CALLs if I
wanted to improve the speed of fdial.)

The result of a WR_GET_COUNTRY_DATA is a WR_COUNTRY_DATA struct,
which (see WLD.DOC) is 74 bytes long.