Short answers, pulled from the story.
IBM announced the first models of its System/360 mainframe family in 1964. This announcement marked a pivotal moment where engineers designed a system to run software written for previous generations without modification.
Backward compatibility describes an operating system or product that allows interoperability with older legacy systems. Engineers distinguish this from forward compatibility, which serves as a design roadmap for future standards and products.
The Zilog Z80 processor demonstrated full backward compatibility with the earlier Intel 8080 processor of 1974. This contrasted with the 8086 family, which was designed with machine-translatability in mind but lacked direct instruction-set compatibility with its 8-bit predecessor.
Sony removed backward compatibility with PlayStation 2 games by eliminating onboard Emotion Engine chips from later revisions. This decision aimed to cut hardware costs and improve console sales figures significantly.
Later versions released from 2011 onwards removed controller and memory card slots effectively ending this ability without modification. Engineers noted the motherboard still contained pads for these connections that could be soldered back in through technical alteration.