An instruction is a statement that becomes executable when the program is assembled and compiled. The assembler translates instructions into machine language bytes and is loaded and executed by the CPU at runtime.
A directive has four components:
Label (optional)
Instruction mnemonic (required)
Operands (usually required)
Comments (optional)
Recently, I have encountered many problems in the process of learning assembly language. This will be updated gradually in the future. This time I will talk about the difference between mov and lea instructions.
1. Regarding whether there is any question about adding []
1. For the mov command:
Whether there is [] does not matter if the variable is, the result is all the value
For example: num dw 2
mov bx,num
mov cx,[num]；bx=cx=2
For registers, [] means the address, but no [] means the value.
For example: num dw 2
mov ax,num
mov bx,ax;bx=2
mov bx,[ax];mov bx;DS:[ax], there may be an error here, in short, just understand the general meaning
2. For the lea instruction:
Is there any [] that doesn't matter if there is a variable, and the result is to take the address of the variable, which is equivalent to a pointer (opposite to mov)
For example: num dw 2
lea ebx,num;
lea eax,[num];ebx=eax
For registers, [] represents the value, but not [] represents the address.
For example: mov eax,2
mov ebx,[eax];ebx=2
mov ebx,eax;eax=address, different from program
Summarize
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