"When Grace Hopper retired from the U.S. Navy as a rear admiral in 1986 at the age of seventy-nine, she was the oldest serving officer in all the armed forces. A mathematician by training and a pioneer in computer science, the eccentric and outspoken Hopper helped propel the navy into the computer age. She was also a superb publicist for the navy, always ready with a good quote for reporters. Yet in spite of her high profile and the fact that she...

The war against U-boats in the Atlantic was won in part by a high-frequency direction finder - called Huff-Duff or HF/DF for short - that could pinpoint the location of radio transmitters. The electronic device was used extensively by the Allies to locate German submarines attacking merchant ships in the Atlantic. Yet it remained little known and understood, while its counterparts, sonar and radar, became household words. The story of HF/DF's development...