Question

Registers R1 and R2 of a computer contains the decimal value 1100 and 500.What is the effective address of the memory operand in each of the following instructions?

i)LOAD  20(R1),R5

ii)MOVE 300,R5

iii)STORE R5,50(R1,R2)

IV)SUBSTRACT(R1)+,R5

Answer 1

1.. 20(R1) = Base Indexed addressing = M[ (R1) + 20] = M[ M[1100] +20] ......{ (R1) is register indirect addressing }

EA=M[1100] +20

 

2... 300 is the effective EA

 

3.. 50(R1,R2)  = M[ M[1110]  + M[500] +50]

EA=M[1110]  + M[500] +50

 

4.. (R1) = M[1100]

EA=1100