What is "bci" while debugging in jdb?

While debugging with jdb on the command line, it shows me a status line after each step that looks like this:

Step completed: "thread=main", [class name].[method], line=10 bci=20

What is bci and how can it be useful to me?

What is the purpose of JDB?

The Java Debugger, jdb, is a simple command-line debugger for Java classes. It is a demonstration of the Java Platform Debugger Architecture that provides inspection and debugging of a local or remote Java Virtual Machine.

Which option is used with JDB to specify find class files?

-sourcepath <dir1:dir2:...> Uses the given path in searching for source files in the specified path. If this option is not specified, the default path of "." is used.

It means byte code index . A single line, even a single Java statement, may translate to several bytecode instructions. The byte code index tells you which bytecode instruction was executed.