A ruling by the U.S. Copyright Office has done little to clear up a year-old legal muddle in the software industry over what parts of a computer program can be protected from imitation and whether a de facto industry standard should even be subject to protection.

The Copyright Office, in an usual effort to establish policy behind granting copyrights as well as the mechanics of getting one, ruled last week that the visual displays on a computer screen can carry a copyright, no matter what kind of software code is used to create those displays.The ruling could go right to the heart of a number of lawsuits that have been filed by software companies over what insiders like to call the "look and feel" issue, but only if courts decide to pay attention, legal experts said.

"Really, only the courts can decide copyrightability," said Ronald Laurie, an attorney with Townsend & Townsend of San Francisco who specializes in intellectual property laws.

"The ruling does not have any direct effect because it is just a statement on how to go about registering for a copyright," he said. "The real issue is whether the courts will pay attention to the Copyright Office."

Traditionally software copyrights have been interpreted by judges as protecting the electronic zeros and ones that make up the computer code, which tells the computer how to make the software run.

That code is invisible to the user and usually is dramatically different for each program, even if the program looks and feels the same to the person working on the machine.

Apple Computer Inc. and Lotus Development Corp. have both filed well-publicized lawsuits charging that their copyrights were violated by companies that developed software programs that looked like theirs, but were based on a completely different underlying code.

Software publishers are unanimous in opposing outright piracy of copyrighted programs, when a piece of software copies the code of another line for line. But there is little agreement on how to approach the hundreds of programs that are variants, or clones, of the bestselling software.

Lotus, Apple and now apparently the Copyright Office say that those variants are not legal if they use the same screen graphics, such as the trash can that represents "omit" on Apple's Macintosh comptuer.

But many software developers argue that new programs always build on existing ones and must be free to use the screen symbols as a jumping off point.

Laurie said he was surprised at the Copyright Office's decision that when a company copyrights a software program, it automatically copyrights the graphic and textual displays produced by the program. If the ruling is upheld by the courts it would mean, for example, that only the Macintosh would be able to use a trash can to signify "omit."

But the trash can, many say, has become an industry standard, as has the graphics used in Lotus's 1-2-3 spreadsheet program, the best-selling software in the world.

Lotus was the first prominent software publisher to file a "look and feel" lawsuit, against two much smaller companies that market programs that are similar to 1-2-3. Lotus charged last year, in an action still pending, that Paperback International Software Inc. and Mosaic Software Inc. violated its copyright by imitating the 1-2-3 user interface - the method by which the user works with the program.

Critics of Lotus charge that the company is being hypocritical in that 1-2-3 was heavily derivative of Visicalc, the first spreadsheet program, which Lotus bought in 1986 and then killed.

Apple has come under much more fire for its lawsuit filed in March against Microsoft Corp. and Hewlett-Packard Co. for copying graphics popularized by the Macintosh. The lawsuit was a surprise to the industry because Apple has licensed much of its software to Microsoft for years, but the computer company charged that Microsoft went beyond the limits set by those licenses on certain display graphics.

Both Apple and Lotus's stock price rose after the Copyright Office's ruling was announced.

Meanwhile, many in the industry worry that this legal conundrum is stifling innovation and ultimately hurting the issue. In fact, most industry analysts and legal experts charged when Apple filed its lawsuit that the company's main goal was to stop its rivals from closing in on its own technological edge.