# Java: CLASSPATH

## Where Java finds programs

A common way to compile and run a simple Java program is with commands like the following.

        javac MyProgram.java
        java MyProgram

Or you may use an IDE that permits you to compile and run. In any case, Java must know, both for compilation and execution of the programs, where to find any library classes that are used. Java (at least after version 1) knows how to find it's own classes, but you have to tell it where to find other libraries you may be using. The standard Microsoft Windows directories are not searched.

You may need to specify a list of directories or jar files where programs can be found by setting the environment variable `CLASSPATH`.

## Setting CLASSPATH on Windows XP

The CLASSPATH variable can be set on Windows XP with the following steps.

- Click the `Start` button in the lower left of the screen.
- Select `Control Panel` from the pop-up menu.
- Choose `System` from the submenu.
- Click the `Advanced` tab.
- Click the `Environment Variables` button near the bottom. You will now see tow lists of variables.
- Look in the `System variables` list for a variable named `CLASSPATH`. If you find it, click `Edit`. If you don't find it, click `New` and enter `CLASSPATH` in the `Variable name` field.
- The `Variable value` field is a list of file paths of directories or `jar` files.

## References

A more complete explanation of `CLASSPATH` can be found in Java Glossary : classpath.