21.   David wrote Ted to tell him the sad news, using a code devised by his increasingly paranoid brother.

22.   Each code would be used to send only one message.

23.   Eltron International Inc. can only hope that businesses keep coming up with such novel ways of using the codes.

24.   Ever listen to a group of really hard-core business travelers rattle off itineraries using airport codes instead of city names?

25.   For instance, I tried to call home for three days, carefully using the code supplied in my room.

26.   He said the C codes were used by the Highway Patrol.

27.   Hospital bills, he explained, are constructed using codes that are intended for insurance companies and government agencies.

28.   If you click on a home page, you can see the HTML programming code used to develop it.

29.   In lieu of the signature form, EZ filers can use a code found on tax materials the IRS mailed to them at the start of the year.

30.   In recent years, with the advent of the ban on nuclear testing, the codes have been used as a substitute for test explosions themselves.