IBM PC compatible computers are those generally similar to the original IBM PC, XT, and AT. Such computers used to be referred to as PC clones, or IBM clones since they almost exactly duplicated all the significant features of the PC, XT, or AT internal design, facilitated by various manufacturers' ability to legally reverse engineer the BIOS through cleanroom design. Columbia Data Products built the first clone of an IBM computer through a cleanroom implementation of its BIOS. Early IBM PC compatibles used the same computer bus as the original PC and AT models, which was later named the ISA Bus when manufacturers developed alternatives to the original IBM standard.
"IBM compatible" is now an historical term since IBM no longer manufactures personal computers.
Descendants of the IBM PC compatibles make up the majority of microcomputers on the market today, although interoperability with the bus structure and peripherals of the original PC, XT or AT may be non-existent.
