A Unix user named Bob can run a Java chess program from his home directory using the command java -classpath /test:/home/bob/downloads/*.jar games.Chess. Given that the CLASSPATH includes /test, where could the Chess.class file be located so that this command works?

Introduction / Context:
Java uses the classpath mechanism to locate compiled class files when running applications. Understanding how the virtual machine maps a fully qualified class name to a location in the file system is important for diagnosing class not found errors. This question describes a specific command line and asks where the Chess.class file could reside for the Java runtime to find it.

Given Data / Assumptions:

• The command is java -classpath /test:/home/bob/downloads/*.jar games.Chess.
• The CLASSPATH contains the directory /test and some jar files in /home/bob/downloads.
• The fully qualified class name is games.Chess.
• We assume standard Java class lookup rules.

Concept / Approach:
When Java loads a class named games.Chess from a directory entry on the classpath, it treats the dots as directory separators. The base directory on the classpath is combined with the package structure to form the path to the class file. Therefore, for the directory /test, the runtime will look for a subdirectory games containing a file named Chess.class. This leads to the path /test/games/Chess.class as a valid location for the class, assuming that /test is on the classpath as given.

Step-by-Step Solution:
Step 1: Identify the fully qualified class name games.Chess and note that games is the package and Chess is the class. Step 2: Recall that Java converts the package name into a directory structure relative to an entry on the classpath. Step 3: Take the directory /test from the given classpath. Step 4: Append the package path games and the file name Chess.class to get /test/games/Chess.class. Step 5: Compare this reasoning with the options and select the one that matches /test/games/Chess.class.

Verification / Alternative check:
You can verify this behaviour by compiling a simple Java class in a package and placing the resulting directory structure under a known classpath directory. Running the program with the correct classpath entry allows the virtual machine to find the class file using the package to directory mapping. Documentation for the java command confirms that directories in the classpath are used as roots for these package based lookups.

Why Other Options Are Wrong:
Option B, /test/Chess.class, would correspond to a class in the default package rather than in the games package, so it does not match the fully qualified name games.Chess. Option C, /home/bob/Chess.class, is not under the listed classpath directories for classes; only jar files in /home/bob/downloads are mentioned. Option D, /usr/lib/games/Chess.class, is not part of the given classpath, so the Java runtime would not look there when resolving the games.Chess class.

Common Pitfalls:
A common mistake is to ignore the package name and assume that any directory on the classpath directly contains class files. Another pitfall is to misinterpret the wildcard in /home/bob/downloads/*.jar as including directories or class files directly, but it only adds jar archives to the classpath. Remember that the mapping from package names to directory structures is central to how Java locates classes at runtime.

Final Answer:
The Chess.class file can be placed at /test/games/Chess.class so that the class games.Chess is found using the given classpath.