What does the R stand for in RAX, RBX, RCX, RDX, RSI, RDI, RBP, RSP?
assembly, cpu-architecture, cpu-registers, x86, x86-64
Solution
I think it's just R for "register", since there are additional registers R8 - R15 on x86-64, and R is a common prefix on many CPU architectures where registers are numbered.
Problem
The x86 assembler language has had to change as the x86 processor architecture has changed from 8bit to 16bit to 32bit and now 64bit. I know that in 32bit assembler register names (EAX, EBX, etc.), the E prefix for each of the names stands for Extended meaning the 32bit form of the register rather than the 16bit form (AX, BX, etc.). What does the R prefix for these register names stand for in 64bit?
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