Q. When running Windows 95, how do I get the mouse to work in DOS mode?

A. The answer involves the operating system you're using (Windows 95) and the central processing unit normally used to run it (Intel).

Years ago, Intel developed the granddaddy of today's processors: the Intel 80286. This CPU imitated earlier chips (8088/8086) and it allowed DOS--the original operating system for PCs--to run faster. The company accomplished this sleight-of-hand with something called "real mode." It was fine, but did not allow access to lots of memory or permit more than one program to run at a time.

Later processors supported "protected mode," which improved memory use and allowed multitasking. Under this mode, each program is assigned an area of memory to use. By staying in that area, it is "protected" from other programs. Microsoft Windows takes advantage of protected mode.

Your Windows machine right now is using small software components called "drivers" to run the mouse. These are all running in protected mode. If you want to use the mouse under DOS, you will need to install real mode DOS drivers for it. When you buy a mouse, you normally get a diskette containing these drivers.

What is the difference between Java and JavaScript?

Not quite like the difference between lightning and lightning bug--but hats off to Samuel Clemens for this great lead-in.

Java is a cross-platform application-development language from Sun Microsystems. The idea behind it is quite simple: enable programmers to write code for programs that will run on a variety of platforms, including Mac, Windows and Unix. Java also is useful for creating small application modules, known as "applets," for use on Web pages.

JavaScript, a separate language that originated at Netscape, has some things in common with Java but is more comparable to languages such as Visual Basic or Perl.

Most readers have heard of something called a "macro." Macros are used in programs to group together commands. For example, instead of writing "Sincerely yours" at the bottom of a letter, you can create a macro that will automatically insert it.

A "script" is very similar to a macro. It takes a few commands and groups them together. When people talk about "scripts" they do not normally refer to manipulating text in a word processing program, they refer to manipulating commands in a programming language.

Under Windows 95, what ".tmp" files can I erase?

If you look on your hard drive, you will see a variety of files that end in "tmp." These are temporary files created by you and Windows 95 and, according to Microsoft, they are not critical and you can erase all of them.

Essentially, a temporary file is a snapshot of information that the user did not save. When you use application programs such as word processors or databases, you are probably creating temporary files on your hard drive. To speed up Web surfing, Web browsers tend to place ".gif" and ".jpg" files on your hard drive as well. If you are not careful, they can become as numerous as Captain Kirk's tribbles.

I normally recommend that users delete any unwanted programs and files on their hard drive to make their system more efficient. My solution is the unheralded Uninstaller 5.1 from CyberMedia ($39.95), available at http://www.cybermedia.com/products/uninstaller/undetails.html. In addition to enabling you to completely remove programs, it has an option that will clean excess files from your hard drive.

John Gilroy of Item Inc. is heard on WAMU-FM radio's "The Computer Guys" at 1 p.m. on the first Tuesday of the month. Send your questions to him in care of The Washington Post, 1150 15th St. NW, Washington, D.C. 20071-5302 or via e-mail at jgilroy@iteminc.com.