X86

x86 is an instruction set architecture (ISA) for the Intel 8086 microprocessor, a chip which was first produced in the late 1970's (get exact date) and is notable for being the chip used in the very first IBM compatible PC sold by IBM beginning in 1983. Remarkably, around this time Intel and Microsoft jointly made a decision to maintain backward compatibility in both hardware and software, with the result that all subsequent "Intel" processor chips could always execute those same instructions, and as well, any program which ran on the original operating system of the first generation of IBM compatible PC continued to execute successfully on later versions of Microsoft operating system.

This decision to maintain backward compatibility of hardware and software laid the groundwork for the subsequent success of the x86 family of microprocessors, and the IBM compatible PC's which contain them.