P's business consists of manufacturing and selling video games. Two of those games are the subjects of this lawsuit, Galaxian, and Pac-Man. D is selling electronic devices that are intended to simulate Galaxian and Pac-Man as well as devices that are designed to be inserted into P's Galaxian game to speed up and otherwise alter the play of the game (speed-up kits). A printed circuit board used in P's Galaxian was shown to the court at the hearing. The board is two-tiered, consisting of a relatively large 'motherboard' which served as the base, and a smaller 'piggyback memory board' mounted on the top of the motherboard. The motherboard contained a microprocessor and two 'character ROMs,' in which the computer programs necessary to create the shapes seen on the screen are stored. ROM stands for read-only memory. The piggyback board is made up of five ROMs on its top side and two sets of twenty-four pins descending out from its bottom. The pins fit into sockets on the motherboard and connect the ROMs on the piggyback board to the microprocessor on the motherboard. The ROMs on the piggyback board contain permanently imprinted computer programs that direct the microprocessor to cause the images created by the character ROMs to appear in certain locations on the television screen. When a player moves the controls of the game an electric signal is sent to the microprocessor, which scans the program ROMs for the predetermined sequence in which the images are to move on the screen. If a player were to move the controls of either a Pac-Man or Galaxian video game in exactly the same way in two different plays of the game, the images on the screen would all move in exactly the same way. Both the games in this suit were created by Namco Limited, a Japanese company. P and Namco entered into a know-how license agreement in which Namco granted P an exclusive license to make and sell the games in the United States. Namco assigned the copyrights of both games to P. On March 6, 1980, P's attorney filed a performing arts application to register the Galaxian game and deposited a videotape, a brochure for the game, and other materials including a written 'Synopsis of Deposit.' The Copyright Office granted the application and issued Certificate of Copyright Registration No. PA 59-977, effective as of March 6, 1980. The certificate states that the work for which the copyright is registered is entitled 'Galaxian' or 'Midway's Galaxian', that the work is an audiovisual work, that Namco is the author of the work, that the work was created in 1979, and that it was first published in Japan on September 15, 1979. P also obtained a Certificate of Copyright Registration No. PA 68-323 specifically for the Galaxian attract mode which was not included in the videotape deposit for PA 59-977, and Certificate of Copyright Registration PA 83-768 for the entirety of the Pac-Man game. For each certificate, Midway submitted a videotape and a written synopsis of the deposit with the application. D sells a speed-up kit, which, when attached to the Galaxian game, modifies the way the images move on the screen. It causes the aliens to move faster and to increase to six the number of aliens that attack the player's ship in formation. The aliens in the sped-up version drop more bombs on the player's ship. The obvious result of attaching the speed-up kit to a Galaxian game is to make the game more difficult to play, dramatically shortening the time that it takes for a player to lose his rocket ships and be forced to insert an additional coin to continue play. D's speed-up kit is made up of a relatively small printed circuit board with five devices called 'EPROMs' (erasable programmable ROMs). Dr. Thomas DeFanti, a professor of computer science at the University of Illinois, compared the two printed versions of the instructions. He found that out of about 10,000 'bytes' of the source code in the two sets of programs, there were only about 488 differences. Dr. DeFanti's conclusion was, 'It is a clear case of copying here.' The second item sold by D is a Puckman circuit board. The only differences between Puckman and Pac-Man games are (1) the names of the ghost characters in D's game are different, (2) the P copyright notice does not appear on D's game, and (3) the name of the game is different. Other than those trivial differences, the games are absolutely identical. D's Puckman printed circuit board contains an error common to P's Pac-Man game. P filed a motion for preliminary injunction and D filed a motion for summary judgment