Where does CMP store the result?
The difference is not stored anywhere. However, the flags register is updated and can be used in a conditional jump, like jump-if-equal ( JE ), most often as the next instruction after the cmp .
What is CMP instruction?
The CMP instruction compares two operands. It is generally used in conditional execution. This instruction basically subtracts one operand from the other for comparing whether the operands are equal or not. It does not disturb the destination or source operands.
How much memory is needed to store a paragraph in the x86 instruction set?
Each segment begins at a multiple of 16 bytes, called a paragraph, from the beginning of the linear (flat) address space.
Does CMP change the registers?
You didn’t specify the processor, but to the best of my knowledge, on any CPU with a CMP instruction, only the flags register is changed. You would have to look at the CPU manual to see exactly what bits are modified. Some CPU’s have a similar instruction, that does an add, instead of a subtract, like the ARM has CMN.
What is the purpose of the x86 assembly language JMP instruction?
In the x86 assembly language, the JMP instruction performs an unconditional jump. Such an instruction transfers the flow of execution by changing the program counter.
What does the AND instruction do?
It does a bit-wise Boolean “and” between two operands. In other words, corresponding bits (bit n in each operand) are anded, in the Boolean operation sense, giving bit n of the result. In Boolean logic, 1 and 1 = 1, but 0 and x (anything else) = 0.
What does Inc do in assembly?
The INC instruction is used for incrementing an operand by one. It works on a single operand that can be either in a register or in memory.
What does $$ mean in x86 assembly?
$ is used to refer to the current address and $$ is used to refer to the address of the start of current section in assembly.
Does CMP set carry flag?
reg, mem, and immed can be 8, 16, or 32 bits. The CMP instruction sets the flags as if it had performed subtraction on the operand.
Which flag register is affected by CMP instruction?
CMP and TEST instructions affect flags only and do not store a result (these instruction are used to make decisions during program execution). These instructions affect these flags only: CF, ZF, SF, OF, PF, AF.
What is the CMP instruction used for?
The cmp instruction is used to perform comparison. It’s identical to the sub instruction except it does not affect operands. It impacts the Zero Flag (ZF) as well as the Carry Flag (CF) as follows:
How complex is the x86 instruction set?
The full x86 instruction set is large and complex (Intel’s x86 instruction set manuals comprise over 2900 pages), and we do not cover it all in this guide. For example, there is a 16-bit subset of the x86 instruction set. Using the 16-bit programming model can be quite complex.
How does CMP perform subtraction and store result?
CMP performs a subtraction but does not store the result. The CF, OF, SF, ZF, AF, and PF flags are set according to the result. I see that you like pain and are using the braindead variant of x86 assembly called ATT-syntax. Show activity on this post. I think i understand it now. This is how i think it goes (borrow flag is set)
How difficult is it to write x86 assembly code in MASM?
MASM uses the standard Intel syntax for writing x86 assembly code. The full x86 instruction set is large and complex (Intel’s x86 instruction set manuals comprise over 2900 pages), and we do not cover it all in this guide. For example, there is a 16-bit subset of the x86 instruction set. Using the 16-bit programming model can be quite complex.