Mov AL,AH in C++ or C

0 Tatrasiel R · April 8, 2015
Lets say I have an integer 20AB

How can I make the integer 2020 by moving the High byte to the Lowbyte place?

I am just going through something, but I need a clear way to represent this in C or C++.


I was thinking, would this work. Can anyone think of a better way?
int Index 0x000020AB;





LOBYTE(Index) = HIBYTE(Index);


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0 Dol Lod · April 9, 2015
Here is one way to do it if you want  0x00002020
int Index=0x000020AB;
Index=(Index>>8); //this gets rid of the AB so you have 0x00000020
Index|=(Index<<8); //this keeps the 20 at the end and assigns the previous // two bytes. now index=0x00002020



I hope this is what you were looking for. Just practice shifting. When I first did it, I could not understand a thing. Now I actually am getting how to use left shifting,right shifting,or,and and xor operation. 

To better understand shifting, I recommend simply using Python's interpreter b/c there is no need to even compile to see how shifting works. 
0 M .A.K · April 9, 2015
The above post is the best way possible and it's using pure C/C++;
but if u'r just looking for clearest way possible so u should dive in Assembly!
so:

#include <stdio.h>
#include <iostream>

using namespace std;

int main() {
    register int index asm("ebx");
    index = 0x20AB;
    __asm__("mov %bh, %bl\n\t");
    cout << hex << index;
    return 0;
}
0 Dol Lod · April 9, 2015
@ M.A.K. 

I don't understand registers and the like that well, but aren't you making an assumption about the OS using Intel x86  instead of something like MIPS or ARM?
0 M .A.K · April 9, 2015
OH ,YIP! I forgot sorry. not only i have that assumption about cpu but also i assume that he/she will use gcc compiler.
this program will run on x64_x86 machines. plus other compilers have different ways of assembly integration in a C/C++ code that might not accept gcc way of doing stuff!
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