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Computer software or simply software is any set of instructions that directs a computer to perform specific operations. Computer software consists of computer programs, libraries and related non-executable data (such as online documentation or digital media). Computer software is non-tangible, contrasted with computer hardware, which is the physical component of computers. Computer hardware and software require each other and neither can be realistically used without the other. At the lowest level, executable code consists of machine language instructions specific to an individual processor—typically a central processing unit (CPU). A machine language consists of groups of binary values signifying processor instructions that change the state of the computer from its preceding state. For example, an instruction may change the value stored in a particular storage location inside the computer—an effect that is not directly observable to the user. An instruction may also (indirectly) cause something to appear on a display of the computer system—a state change which should be visible to the user. The processor carries out the instructions in the order they are provided, unless it is instructed to "jump" to a different instruction, or interrupted. Software written in a machine language is known as "machine code". However, in practice, software is usually written in high-level programming languages that are easier and more efficient for humans to use (closer to natural language) than machine language. High-level languages are translated into machine language using a compiler or an interpreter or a combination of the two. Software may also be written in a low-level assembly language, essentially, a vaguely mnemonic representation of a machine language using a natural language alphabet. Assembly language is translated into machine language using an assembler. ==History== (詳細はalgorithm) for what would have been the first piece of software was written by Ada Lovelace in the 19th century, for the planned analytical engine. However, neither the analytical engine nor any software for it were ever created. The first theory about software—prior to the creation of computers as we know them today—was proposed by Alan Turing in his 1935 essay ''Computable numbers with an application to the Entscheidungsproblem'' (decision problem). This eventually led to the creation of the twin academic fields of computer science and software engineering, which both study software and its creation. Computer science is more theoretical (Turing's essay is an example of computer science), whereas software engineering is focused on more practical concerns. However, prior to 1946, software as we now understand it—programs stored in the memory of stored-program digital computers—did not yet exist. The very first electronic computing devices were instead rewired in order to "reprogram" them. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Software」の詳細全文を読む スポンサード リンク
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