Sloviter, Circuit Judge.

INTRODUCTION

Apple Computer, Inc. appeals from the district court's denial of a motion to preliminarily enjoin Franklin Computer Corp. from infringing the copyrights Apple holds on fourteen computer programs. ***

In this case the district court denied the preliminary injunction, inter alia, because it had "some doubt as to the copyrightability of the programs." Apple Computer, Inc. v. Franklin Computer Corp., 545 F.Supp. 812, 812 (E.D.Pa.1982). This legal ruling is fundamental to all future proceedings in this action and, as the parties and amici curiae seem to agree, has considerable significance to the computer services industry. Because we conclude that the district court proceeded under an erroneous view of the applicable law, we reverse the denial of the preliminary injunction and remand.

FACTS AND PROCEDURAL HISTORY

Apple, one of the computer industry leaders, manufactures and markets personal computers (microcomputers), related peripheral equipment such as disk drives (peripherals), and computer programs (software). *** One of the byproducts of Apple's success is the independent development by third parties of numerous computer programs which are designed to run on the Apple II computer.

Franklin, the defendant below, manufactures and sells the ACE 100 personal computer. *** The ACE 100 was designed to be "Apple compatible," so that peripheral equipment and software developed for use with the Apple II computer could be used in conjunction with the ACE 100. Franklin's copying of Apple's operating system computer programs in an effort to achieve such compatibility precipitated this suit. ***

Computer programs can be categorized by function as either application programs or operating system programs. Application programs usually perform a specific task for the computer user, such as word processing, checkbook balancing, or playing a game. In contrast, operating system programs generally manage the internal functions of the computer or facilitate use of application programs. The parties agree that the fourteen computer programs at issue in this suit are operating system programs.

Apple filed suit in the United States District Court for the Eastern District of Pennsylvania pursuant to 28 U.S.C. s 1338 on May 12, 1982, alleging that Franklin was liable for copyright infringement of the fourteen computer programs ***

After expedited discovery, Apple moved for a preliminary injunction to restrain Franklin from using, copying, selling, or infringing Apple's copyrights. The district court held a three day evidentiary hearing limited to the copyright infringement claims. ***

Franklin did not dispute that it copied the Apple programs. Its witness admitted copying each of the works in suit from the Apple programs. Its factual defense was directed to its contention that it was not feasible for Franklin to write its own operating system programs. David McWherter, now Franklin's vice-president of engineering, testified he spent 30-40 hours in November 1981 making a study to determine if it was feasible for Franklin to write its own Autostart ROM program and concluded it was not because "there were just too many entry points in relationship to the number of instructions in the program." Entry points at specific locations in the program can be used by programmers to mesh their application programs with the operating system program. McWherter concluded that use of the identical signals was necessary in order to ensure 100% compatibility with application programs created to run on the Apple computer. He admitted that he never attempted to rewrite Autostart ROM and conceded that some of the works in suit (i.e. Copy, Copy A, Master Create, and Hello) probably could have been rewritten by Franklin. Franklin made no attempt to rewrite any of the programs prior to the lawsuit except for Copy, although McWherter testified that Franklin was "in the process of redesigning" some of the Apple programs and that "[w]e had a fair degree of certainty that that would probably work." Apple introduced evidence that Franklin could have rewritten programs, including the Autostart ROM program, and that there are in existence operating programs written by third parties which are compatible with Apple II.

Franklin's principal defense at the preliminary injunction hearing and before us is primarily a legal one, directed to its contention that the Apple operating system programs are not capable of copyright protection.

The district court denied the motion for preliminary injunction by order and opinion dated July 30, 1982. Apple moved for reconsideration in light of this court's decision in Williams Electronics, Inc. v. Arctic International, Inc., 685 F.2d 870 (3d Cir.1982), which was decided August 2, 1982, three days after the district court decision. The district court denied the motion for reconsideration. ***

Copyrightability of a Computer Program Expressed in Object Code

Certain statements by the district court suggest that programs expressed in object code, as distinguished from source code, may not be the proper subject of copyright. We find no basis in the statute for any such concern. Furthermore, our decision in Williams Electronics, Inc. v. Arctic International, Inc., supra, laid to rest many of the doubts expressed by the district court.***

We considered the issue of copyright protection for a computer program in Williams Electronics, Inc. v. Arctic International, Inc., and concluded that "the copyrightability of computer programs is firmly established after the 1980 amendment to the Copyright Act." 685 F.2d at 875. At issue in Williams were not only two audiovisual copyrights to the "attract" and "play" modes of a video game, but also the computer program which was expressed in object code embodied in ROM and which controlled the sights and sounds of the game. Defendant there had argued "that when the issue is the copyright on a computer program, a distinction must be drawn between the 'source code' version of a computer program, which ... can be afforded copyright protection, and the 'object code' stage, which ... cannot be so protected," an argument we rejected. Id. at 876.

The district court here questioned whether copyright was to be limited to works "designed to be 'read' by a human reader [as distinguished from] read by an expert with a microscope and patience", 545 F.Supp. at 821. The suggestion that copyrightability depends on a communicative function to individuals stems from the early decision of White-Smith Music Publishing Co. v. Apollo Co., 209 U.S. 1, 28 S.Ct. 319, 52 L.Ed. 655 (1908), which held a piano roll was not a copy of the musical composition because it was not in a form others, except perhaps for a very expert few, could perceive. *** However, it is clear from the language of the 1976 Act and its legislative history that it was intended to obliterate distinctions engendered by White-Smith.

Under the statute, copyright extends to works in any tangible means of expression "from which they can be perceived, reproduced, or otherwise communicated, either directly or with the aid of a machine or device." 17 U.S.C. s 102(a) (emphasis added). Further, the definition of "computer program" adopted by Congress in the 1980 amendments is "sets of statements or instructions to be used directly or indirectly in a computer in order to bring about a certain result." 17 U.S.C. s 101 (emphasis added). As source code instructions must be translated into object code before the computer can act upon them, only instructions expressed in object code can be used "directly" by the computer. ***

The defendant in Williams had also argued that a copyrightable work "must be intelligible to human beings and must be intended as a medium of communication to human beings," id. at 876-77. We reiterate the statement we made in Williams when we rejected that argument: "[t]he answer to defendant's contention is in the words of the statute itself." 685 F.2d at 877.

The district court also expressed uncertainty as to whether a computer program in object code could be classified as a "literary work." However, the category of "literary works", one of the seven copyrightable categories, is not confined to literature in the nature of Hemingway's For Whom the Bell Tolls. The definition of "literary works" in section 101 includes expression not only in words but also "numbers, or other ... numerical symbols or indicia", thereby expanding the common usage of "literary works." *** Thus a computer program, whether in object code or source code, is a "literary work" and is protected from unauthorized copying, whether from its object or source code version. ***

Just as the district court's suggestion of a distinction between source code and object code was rejected by our opinion in Williams issued three days after the district court opinion, so also was its suggestion that embodiment of a computer program on a ROM, as distinguished from in a traditional writing, detracts from its copyrightability. In Williams we rejected the argument that "a computer program is not infringed when the program is loaded into electronic memory devices (ROMs) and used to control the activity of machines." 685 F.2d at 876. Defendant there had argued that there can be no copyright protection for the ROMs because they are utilitarian objects or machine parts. We held that the statutory requirement of "fixation", the manner in which the issue arises, is satisfied through the embodiment of the expression in the ROM devices. ***

Copyrightability of Computer Operating System Programs

We turn to the heart of Franklin's position on appeal which is that computer operating system programs, as distinguished from application programs, are not the proper subject of copyright "regardless of the language or medium in which they are fixed." Brief of Appellee at 15 (emphasis deleted). Apple suggests that this issue too is foreclosed by our Williams decision because some portion of the program at issue there was in effect an operating system program. Franklin is correct that this was not an issue raised by the parties in Williams and it was not considered by the court. Thus we consider it as a matter of first impression.

Franklin contends that operating system programs are per se excluded from copyright protection under the express terms of section 102(b) of the Copyright Act, and under the precedent and underlying principles of Baker v. Selden, 101 U.S. 99, 25 L.Ed. 841 (1879). These separate grounds have substantial analytic overlap.

In Baker v. Selden, plaintiff's testator held a copyright on a book explaining a bookkeeping system which included blank forms with ruled lines and headings designed for use with that system. Plaintiff sued for copyright infringement on the basis of defendant's publication of a book containing a different arrangement of the columns and different headings, but which used a similar plan so far as results were concerned. The Court, in reversing the decree for the plaintiff, concluded that blank account-books were not the subject of copyright and that "the mere copyright of Selden's book did not confer upon him the exclusive right to make and use account-books, ruled and arranged as designated by him and described and illustrated in said book." Id. at 107. The Court stated that copyright of the books did not give the plaintiff the exclusive right to use the system explained in the books, noting, for example, that "copyright of a work on mathematical science cannot give to the author an exclusive right to the methods of operation which he propounds." Id. at 103.

Franklin reads Baker v. Selden as "stand[ing] for several fundamental principles, each presenting ... an insuperable obstacle to the copyrightability of Apple's operating systems." It states: First, Baker teaches that use of a system itself does not infringe a copyright on the description of the system. Second, Baker enunciates the rule that copyright does not extend to purely utilitarian works. Finally, Baker emphasizes that the copyright laws may not be used to obtain and hold a monopoly over an idea. In so doing, Baker highlights the principal difference between the copyright and patent laws--a difference that is highly pertinent in this case. Brief of Appellee at 22.

Section 102(b) of the Copyright Act, the other ground on which Franklin relies, appeared first in the 1976 version, long after the decision in Baker v. Selden. It provides: In no case does copyright protection for an original work of authorship extend to any idea, procedure, process, system, method of operation, concept, principle, or discovery, regardless of the form in which it is described, explained, illustrated, or embodied in such work. It is apparent that section 102(b) codifies a substantial part of the holding and dictum of Baker v. Selden. ***

We turn to consider the two principal points of Franklin's argument.

1. "Process", "System" or "Method of Operation"

Franklin argues that an operating system program is either a "process", "system", or "method of operation" and hence uncopyrightable. Franklin correctly notes that underlying section 102(b) and many of the statements for which Baker v. Selden is cited is the distinction which must be made between property subject to the patent law, which protects discoveries, and that subject to copyright law, which protects the writings describing such discoveries. However, Franklin's argument misapplies that distinction in this case. Apple does not seek to copyright the method which instructs the computer to perform its operating functions but only the instructions themselves. The method would be protected, if at all, by the patent law, an issue as yet unresolved. ***

Franklin's attack on operating system programs as "methods" or "processes" seems inconsistent with its concession that application programs are an appropriate subject of copyright. Both types of programs instruct the computer to do something. Therefore, it should make no difference for purposes of section 102(b) whether these instructions tell the computer to help prepare an income tax return (the task of an application program) or to translate a high level language program from source code into its binary language object code form (the task of an operating system program such as "Applesoft"). Since it is only the instructions which are protected, a "process" is no more involved because the instructions in an operating system program may be used to activate the operation of the computer than it would be if instructions were written in ordinary English in a manual which described the necessary steps to activate an intricate complicated machine. There is, therefore, no reason to afford any less copyright protection to the instructions in an operating system program than to the instructions in an application program.

Franklin's argument, receptively treated by the district court, that an operating system program is part of a machine mistakenly focuses on the physical characteristics of the instructions. But the medium is not the message. We have already considered and rejected aspects of this contention in the discussion of object code and ROM. The mere fact that the operating system program may be etched on a ROM does not make the program either a machine, part of a machine or its equivalent. Furthermore, as one of Franklin's witnesses testified, an operating system does not have to be permanently in the machine in ROM, but it may be on some other medium, such as a diskette or magnetic tape, where it could be readily transferred into the temporary memory space of the computer. In fact, some of the operating systems at issue were on diskette. ***

Franklin also argues that the operating systems cannot be copyrighted because they are "purely utilitarian works" and that Apple is seeking to block the use of the art embodied in its operating systems. This argument stems from the following dictum in Baker v. Selden: The very object of publishing a book on science or the useful arts is to communicate to the world the useful knowledge which it contains. But this object would be frustrated if the knowledge could not be used without incurring the guilt of piracy of the book. And where the art it teaches cannot be used without employing the methods and diagrams used to illustrate the book, or such as are similar to them, such methods and diagrams are to be considered as necessary incidents to the art, and given therewith to the public; not given for the purpose of publication in other works explanatory of the art, but for the purpose of practical application. 101 U.S. at 103.

We cannot accept the expansive reading given to this language by some courts ***. Although a literal construction of this language could support Franklin's reading that precludes copyrightability if the copyright work is put to a utilitarian use, that interpretation has been rejected by a later Supreme Court decision. In Mazer v. Stein, 347 U.S. 201, 218, 74 S.Ct. 460, 471, 98 L.Ed. 630 (1954), the Court stated: "We find nothing in the copyright statute to support the argument that the intended use or use in industry of an article eligible for copyright bars or invalidates its registration. We do not read such a limitation into the copyright law." Id. at 218, 74 S.Ct. at 471. ***

Perhaps the most convincing item leading us to reject Franklin's argument is that the statutory definition of a computer program as a set of instructions to be used in a computer in order to bring about a certain result, 17 U.S.C. s 101, makes no distinction between application programs and operating programs. Franklin can point to no decision which adopts the distinction it seeks to make. ***

2. Idea/Expression Dichotomy

Franklin's other challenge to copyright of operating system programs relies on the line which is drawn between ideas and their expression. Baker v. Selden remains a benchmark in the law of copyright for t he reading given it in Mazer v. Stein, supra, where the Court stated, "Unlike a patent, a copyright gives no exclusive right to the art disclosed; protection is given only to the expression of the idea--not the idea itself." 347 U.S. at 217, 74 S.Ct. at 470 (footnote omitted).

The expression/idea dichotomy is now expressly recognized in section 102(b) which precludes copyright for "any idea." This provision was not intended to enlarge or contract the scope of copyright protection but "to restate ... that the basic dichotomy between expression and idea remains unchanged." H.R.Rep. No. 1476, supra, at 57, reprinted in 1976 U.S.Code Cong. & Ad.News at 5670. The legislative history indicates that section 102(b) was intended "to make clear that the expression adopted by the programmer is the copyrightable element in a computer program, and that the actual processes or methods embodied in the program are not within the scope of the copyright law." Id.

Many of the courts which have sought to draw the line between an idea and expression have found difficulty in articulating where it falls. *** We *** focus on whether the idea is capable of various modes of expression. If other programs can be written or created which perform the same function as an Apple's operating system program, then that program is an expression of the idea and hence copyrightable. In essence, this inquiry is no different than that made to determine whether the expression and idea have merged, which has been stated to occur where there are no or few other ways of expressing a particular idea. ***

The district court made no findings as to whether some or all of Apple's operating programs represent the only means of expression of the idea underlying them. Although there seems to be a concession by Franklin that at least some of the programs can be rewritten, we do not believe that the record on that issue is so clear that it can be decided at the appellate level. Therefore, if the issue is pressed on remand, the necessary finding can be made at that time.

Franklin claims that whether or not the programs can be rewritten, there are a limited "number of ways to arrange operating systems to enable a computer to run the vast body of Apple-compatible software", Brief of Appellee at 20. This claim has no pertinence to either the idea/expression dichotomy or merger. The idea which may merge with the expression, thus making the copyright unavailable, is the idea which is the subject of the expression. The idea of one of the operating system programs is, for example, how to translate source code into object code. If other methods of expressing that idea are not foreclosed as a practical matter, then there is no merger. Franklin may wish to achieve total compatibility with independently developed application programs written for the Apple II, but that is a commercial and competitive objective which does not enter into the somewhat metaphysical issue of whether particular ideas and expressions have merged.

In summary, Franklin's contentions that operating system programs are per se not copyrightable is unpersuasive. The other courts before whom this issue has been raised have rejected the distinction. *** We believe that the 1980 amendments reflect Congress' receptivity to new technology and its desire to encourage, through the copyright laws, continued imagination and creativity in computer programming. Since we believe that the district court's decision on the preliminary injunction was, to a large part, influenced by an erroneous view of the availability of copyright for operating system programs and unnecessary concerns about object code and ROMs, we must reverse the denial of the preliminary injunction and remand for reconsideration. ***