A textbook or coursebook is a manual of instruction in any branch of study. Textbooks are produced according to the demands of educational institutions. Schoolbooks are textbooks and other books used in schools. Although most textbooks are only published in printed format, many are now available as online electronic books.HistoryThe ancient Greeks wrote texts intended for education. The modern textbook has its roots in the standardization made possible by the printing press. Johannes Gutenberg himself may have printed editions of Ars Minor, a schoolbook on Latin grammar by Aelius Donatus. Early textbooks were used by tutors and teachers, who used the books as instructional aids (e.g., alphabet books), as well as individuals who taught themselves.The Greek philosopher Plato lamented the loss of knowledge because the media of transmission were changing. Before the invention of the Greek alphabet 2,500 years ago, knowledge and stories were recited aloud, much like Homer's epic poems. The new technology of writing meant stories no longer needed to be memorized, a development Socrates feared would weaken the Greeks' mental capacities for memorizing and retelling. (Ironically, we know about Socrates' concerns only because they were written down by his student Plato in his famous Dialogues.)The next revolution for books came with the 15th-century invention of printing with changeable type. The invention is attributed to German metalsmith Johannes Gutenberg, who cast type in molds using a melted metal alloy and constructed a wooden-screw printing press to transfer the image onto paper.