where to place ah or al ?

[popey]

hello

i have a small confusion.....when we write mov ah,0x0e why do we move 0x0e to ah not to al...similarly for many other mov instructions do i always need to remember such things or there is any reason

[Combuster]

Does it make a difference to send mail to your left or right neighbour?

[CodeCat]

al and ah are two distinct registers, just as for example eax and ebx are. So ask yourself the same question about eax and ebx, and obviously it makes no sense anymore.

[Zenith]

However, don't forget that al and ah make up the lower and higher 8 bits of ax, respectively. You'd do operations on ah if you only wanted to change the contents of the high 8 bits of ax.

Hope this helps!