1. a topic sentence
TOPIC Controlling idea
Back in 1983 when IBM was putting out its first PCs, many people did not foresee the Millenium problem.
2. Supporting sentences develop the topic sentence
The first PCs had a two-digit date set in their Real Time Clock (RTC). When DOS booted up .....
All this was OK back in 1983 as the lifetime of any one PC was not expected to approach the Millenium.
EXAMPLE PARAGRAPH: taken from http://cctc2.commnet.edu/grammar
Through the centuries rats have managed to survive all our efforts to destroy them. We have poisoned them and trapped them. We have fumigated, flooded, and burned them. We have tried germ warfare. Some rats even survived atomic bomb tests conducted on Entwetok atoll in the Pacific after World War II. In spite of all our efforts, these enemies of ours continue to prove that they are the most indestructible of pests.