Question

Assume that the DS register contains 0100 and register SI contains 0020. What is the result of following instruction LDS DI, [SI] Where the content of memory location is as follows:

Answer 1

LDS : Load Pointer using DS, i.e Load the memory Double Word into word register and DS

Note: The word Double Word

Here LDS DI, [SI] , means using the SI address the data will be copied to DI as well as DS

SI contains 0020 and DS contains 0100 : We have to find out the Memory adress to access , for that we use :-
1. Shift DS content left wise by 1 bit i.e 0100 will become 1000
2. Add the content 1000 and SI we get 1000 + 0020 = 1020   

So we will start referring from address 1020 ,

From the Table we can see that Adress 1020 has 13 in the memory location.

From the Table we can see that Adress 1021 has 14 in the memory location.

From the Table we can see that Adress 1022 has 15 in the memory location.

From the Table we can see that Adress 1023 has 16 in the memory location.

So double word has to be copied into DS and DI

First DI then DS

DI will have 14 13

DS will have 16 15

Thanks, I hope it clarifies