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On the original IBM Personal Computer, and the IBM PCjr, an interface was provided to allow the use of a compact cassette tape recorder to load and save data and programs. It was common for users of home computer of the time, such as the Apple II, Commodore 64 and BBC Micro, to save use cassette tape for storage if they could not afford a floppy disk drive, and in many cases there was a wide range of commercial software available on tape. This however was not the case with the IBM PC - very few were shipped without at least one floppy disk drive, and apart from one diagnostic tape available from IBM,〔("Diagnostics for IBM Personal Computer 1.02 (Cassette)" )〕 there seems never to have been software sold on tape. An IBM PC with just an external cassette recorder for storage could only use the built-in ROM BASIC as their operating system, which supported cassette operations. IBM PC DOS had no support for cassette tape. The IBM PCjr was also seldom sold without a floppy disk drive, but it also had two ROM cartridge slots on the front of the unit - a much more convenient and reliable option for loading software. No market developed for commercial product distribution on cassette tape and the cassette interface was dropped on the subsequent IBM XT. ==Using from software== BIOS interrupt call 15h routines were documented in the technical reference manual that would turn the cassette motor on and off, and read or write data. Data was written with a lead-in section, and formatted in 256-byte blocks with a 2-byte CRC.〔 Programmers could also operate the cassette relay by writing to its I/O address. The cassette, disk, and advanced versions of IBM BASIC included statements for cassette operations, but these features only worked if the machine had a cassette port. 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「IBM cassette tape」の詳細全文を読む スポンサード リンク
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