Judge William Alsup of the U.S. District Court in San Francisco was given an overview of Java and why it was invented, and an explanation of terms such as bytecode, compiler, class libraries and machine-readable code.

The point was to prepare him for a claim construction conference (also called a Markman hearing) in two weeks, where he'll have to sort out disputes between the two sides about how language in Oracle's Java patents should be interpreted. It should also be useful background for him if the two sides don't settle and the case makes it to trial.

Oracle sued Google last August, contending its open-source Android operating system violates Java patents and copyrights that Oracle inherited when it bought Sun Microsystems. Google denies any wrongdoing and has characterized the case as an attack on open source.

Alsup listened attentively from the bench in his courtroom as the two sides, using projectors, each spent 30 minutes describing technologies at issue in the case.

The judge showed at least an elementary understanding of computers. At one point an attorney for Google, Scott Weingaertner, described how a typical computer is made up of applications, an OS and the hardware underneath. "I understand that much," Alsup said, asking him to move on.