title: What do the E and R prefixes stand for in the names of Intel 32-bit and 64-bit registers?
body: <p>The 32-bit register names start with an E and the 64-bit ones start with an R. What do the E and R stand for? Is there a reason for choosing these alphabets?</p>
  
  <p>Also, in 64-bit registers, too, we can see in any low-level debugger such as Windbg that the right-most bits are still referred to by the same name as that of the 64-bit register except the name starts with an E. For e.g. the right-most 32 bits of the RAX register in a 64-bit system is referred to as EAX.</p>
  
  <p>So, do the E and R stand for something? And also, why the suffix X for register?</p>