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And the X also stands for extended.
by BorisTheBrave 7y ago
And the X also stands for extended.
- Kranar 7y agoAlternatively the X is a very old assembly notation for "pair". 8-bit registers on 8080 processors could be paired together to work as a single register. Operations performed on these register pairs used the letter X. You can look here at the original 8080 reference manual: https://altairclone.com/downloads/manuals/8080%20Programmers%20Manual.pdf https://altairclone.com/downloads/manuals/8080%20Programmers... For example page 4 lists the name of instructions, INR is "increment register" while INX is "increment register pair", similar notation is used for several other instructions where the X is the register paired version of an instruction. In the case of the AX register, it likely just refers to the pair of AH and AL registers. At any rate, it's really interesting glancing over the various 8086 reference manuals. Gives me a deep sense of appreciation for how far things have come and how things have managed to build upon what are otherwise some very simple and fundamental building blocks.