I am confused by this question: What is the value stored in register 0 after instruction “LEA R0,A"
is executed? How come the answer is x370C ? I reckon it is supposed to load the address of A into R0? If so how do we know the address? Can someone please help? Many thanks!
.ORIG X3700
LEA R0, A
LDI R2, C LDR R3, R0, 2
AND R1, R1, #0
IN
ST R0, D
JSR F
HALT
F LD R1, B
ADD R1, R1, #1
BRp F
RET
A .FILL X1234
B .FILL X370B
C .FILL X370C
D .BLKW 2
E .STRINGZ "ABCD"
G .FILL X1234
.END
The origin of the code is x3700
, and you have 12 instructions, so the address of A
will be x3700 + x0C = x370C
. As you guessed, LEA R0,A
loads the address of A
into R0
, so R0
will contain x370C
after that first instruction has been executed.
.ORIG X3700
3700 LEA R0, A
3701 LDI R2, C
3702 LDR R3, R0, 2
...
370b RET
370c A .FILL X1234
...