8086 assembly language

what is the significance of

mov ax,@dat开发者_Python百科a

Why do we write it?

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Usually that line would be followed by:

mov ds,ax

E.g.:

mov ax,@data
mov ds,ax

...which sets the ds (data segment) register to point to the data segment created by the program launcher.

I'm not having much luck finding a good link for you other than the WP link above (my search-fu must be weak this morning), but basically, the x86 memory architecture is a segmented architecture, where different segments can be defined as having separate purposes (code, data, statically-initialized data, etc.). The processor then does some useful things for us, like preventing our executing data rather than code.