EAX is the full 32-bit value; AX is the lower 16-bits; AL is the lower 8 bits; AH is the bits 8 through 15 (zero-based), the top half of AX; So AX is composed of AH:AL halves, and is itself the low half of EAX. (The upper half of EAX isn't directly accessible as a 16-bit register; you can shift or rotate EAX if you want to get at it.)

Nov 11, 2022 · Are EAX, EBX, and ECX just variables or do they all have a unique specific use other than storing values? These are the different processor registers. There are no variables in assembly language. You should read a thorough introduction into assembly to …

Jul 7, 2017 · Registers like eax, ebx, etc are the 32-bit registers which exist both in the original 32-bit x86 ISA, as well as the 64-bit x86-64. If your book refers only to those registers, it is likely that it doesn't cover the 64-bit extension (perhaps it was written before it).

The sub-register AX allows us to access the lower 16 bits of EAX. And within AX are the two 8-bit sub-registers, AH and AL. But you may also have noticed that there’s a blank area to the lower-left of EAX.

Mar 20, 2020 · Usually, x86 tutorials don’t spend much time explaining the historical perspective of design and naming decisions. When learning x86 assembly, you’re usually told something along the lines: Here’s EAX. It’s a register. Use it. So, what exactly do those letters stand for? E–A–X. I’m afraid there’s no short answer! We’ll have to go back to 1972…

eax is the 32-bit, "int" size register. It was added in 1985 during the transition to 32-bit processors with the 80386 CPU. I'm in the habit of using this register size, since they also work in 32 bit mode, although I'm trying to use the longer rax registers for …

AX is the primary accumulator; it is used in input/output and most arithmetic instructions. For example, in multiplication operation, one operand is stored in EAX or AX or AL register according to the size of the operand. BX is known as the base …

Different names (e.g. ax vs. eax vs. rax) refer to different parts of the same register

For example, the least significant 2 bytes of EAX can be treated as a 16-bit register called AX. The least significant byte of AX can be used as a single 8-bit register called AL , while the most significant byte of AX can be used as a single 8-bit register called AH .

Mar 22, 2020 · Usually, x86 tutorials don’t spend much time explaining the historical perspective of design and naming decisions. When learning x86 assembly, you’re usually told something along the lines: Here’s EAX. It’s a register. Use it. So, what exactly do those letters stand for? E–A–X. I’m afraid there’s no short answer!