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What is the assembler syntax to determine which of two numbers is greater?
What is the lower level (machine code) for it? Can we go even lower? Once we get to the bit level, what happens? How is it represented in 0's and 1's?
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As already mentioned, usually the comparison is done through subtraction.
In assembly, all branching is done using two types of instruction: A compare instruction, like "cmp", compares two values. Internally, it does this by subtracting them. A conditional jump instruction, like "je" (jump-if-equal), does a goto somewhere if the two values satisfy the right condition.
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.
In TASM (x86 assembly) it can look like this:
cmp BL, BH
je EQUAL ; BL = BH
jg GREATER ; BL > BH
jmp LESS ; BL < BH
in this case it compares two 8bit numbers that we temporarily store in the higher and the lower part of the register B. Alternatively you might also consider using jbe (if BL <= BH) or jge/jae (if BL >= BH).
Hopefully someone finds it helpful :)
103
First a CMP (comparison) instruction is called then one of the following:
jle - jump to line if less than or equal to
jge - jump to line if greater than or equal to
The lowest assembler works with is bytes, not bits (directly anyway). If you want to know about bit logic you'll need to take a look at circuit design.
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