AX is usually called accumulator register , or just accumulator. Most of arithmatical operations are done with AX. Sometimes other general purpose registers can also be involved in arithmatical operation, such as DX. The register BX is usually called base register. The common use is to do array operations.
What is the origin of AX register?
The X in AX meant to be a placeholder that stood for both H and L . This is in a way similar to how much later the “x” in x86 was meant to refer to 8086, 80186, 80286, etc. Since 8008 had seven 8-bit registers, they could be mapped well to the eight 8086 registers, with one to spare.
What is a BX register?
BX – This is the base register . It is of 16 bits and is divided into two 8-bit registers BH and BL to also perform 8-bit instructions. It is used to store the value of the offset.
What is Al and AX?
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) So AX is composed of AH:AL halves, and is itself the low half of EAX.
What is the difference between EAX and AX?
eax is the 32-bit, “int” size register. It was added in 1985 during the transition to 32-bit processors with the 80386 CPU. ... ax is the 16-bit, “short” size register . It was added in 1979 with the 8086 CPU, but is used in DOS or BIOS code to this day.
What is the purpose of AX register?
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 register, as it could be used in indexed addressing.
What are the types of registers?
- MAR Register. The full form of MAR is the memory address register. ...
- MDR. The full form of MDR register is a memory data register. ...
- MBR. The full form of MBR is the memory buffer register. ...
- PC. The full form of PC is the program counter register. ...
- Accumulator. ...
- Index Register. ...
- Instruction Register.
What do you mean by ax?
(Entry 1 of 4) 1 : a cutting tool that consists of a heavy edged head fixed to a handle with the edge parallel to the handle and that is used especially for felling trees and chopping and splitting wood. 2 : a hammer with a sharp edge for dressing (see dress entry 1 sense 6e) or spalling stone.
What does R stand for in Rax?
At the same time Intel was introducing additional, general purpose registers . Using a common industry naming convention for general purpose register, the letter R, followed by a number was an easy decision.
Which is type of general purpose register?
The general purpose registers are divided into two categories. Four registers, AX, BX, CX, and DX, are classified as data registers .
What does EAX stand for?
| Acronym Definition | EAX Environment Audio Extension | EAX Environmental Audio Extensions | EAX Electronic Automatic Exchange | EAX Environmental Audio Experience |
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Is EAX general register?
The EAX, EBX, ECX, EDX, EBP, EDI, and ESI registers are all 32-bit general-purpose registers , used for temporary data storage and memory access. Some of CPU instructions modify specific registers.
What is the difference between the EAX AX AH and AL registers?
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. These names refer to the same physical register.
What does test EAX EAX do?
TEST sets the zero flag, ZF , when the result of the AND operation is zero. If two operands are equal, their bitwise AND is zero when both are zero. TEST also sets the sign flag, SF , when the most significant bit is set in the result, and the parity flag, PF , when the number of set bits is even.
What are registers used for?
Registers are small amounts of high-speed memory contained within the CPU. They are used by the processor to store small amounts of data that are needed during processing , such as: the address of the next instruction to be executed.
What is 32-bit register?
Most computers made in the 1990s and early 2000s were 32-bit machines. The CPU register stores memory addresses , which is how the processor accesses data from RAM. One bit in the register can reference an individual byte in memory, so a 32-bit system can address a maximum of 4 GB (4,294,967,296 bytes) of RAM.
