What does ESP mean in assembly?

ESP = ? stack pointer

What does **E** stand for here?

**UPDATE**

RSP for 64bit?

What does `R` mean here?

`E` stands for `Extended`

> With the advent of the 32-bit 80386 processor, the 16-bit general-purpose registers, base registers, index registers, instruction pointer, and FLAGS register, but not the segment registers, were expanded to 32 bits. This is represented by prefixing an **"E" (for Extended)** to the register names in x86 assembly language.

[Source][1]


[1]:

[To see links please register here]

Perhaps for consistency with the other 32-bit registers: `EAX`, `EBX` etc.

For those, `E` means "extended" - i.e. to 32 bits (the 16-bit versions are called `AX`, `BX` etc.)

P.S. according to [The Free Dictionary][1], `ESP` stands for Extended Stack Pointer.


[1]:

[To see links please register here]

E means Extended. If you have SP 16bit, so ESP should be 32bit.

R is just for "register", with the new registers called just r8-r15. Since the old ones also needed names for their extended versions, the e was just swapped to r.