Answer:Here's an LC-3 program that accomplishes the task you described:
Step-by-step explanation:
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ORIG x3000
AND R1, R1, #0 ; initialize R1 to 0
ADD R4, R2, #-1 ; subtract 1 from R2
ADD R5, R3, #-1 ; subtract 1 from R3
BRzp both_positive ; if both R2 and R3 are positive, go to both_positive
BRn R2_negative ; if R2 is negative, go to R2_negative
BRn R3_negative ; if R3 is negative, go to R3_negative
both_positive:
ADD R4, R4, R5 ; subtract R5 from R4
BRn R2_larger ; if R2 > R3, go to R2_larger
BRz equal ; if R2 = R3, go to equal
ADD R1, R3, #0 ; if R3 > R2, store R3 in R1
BRnzp done ; go to done
R2_negative:
ADD R4, R4, R5 ; subtract R5 from R4
BRn R2_larger ; if -R2 > R3, go to R2_larger
ADD R1, R3, #0 ; if R3 > -R2, store R3 in R1
BRnzp done ; go to done
R3_negative:
ADD R4, R4, R5 ; subtract R5 from R4
BRzp R2_larger ; if R2 > -R3, go to R2_larger
ADD R1, R2, #0 ; if -R3 > R2, store R2 in R1
BRnzp done ; go to done
R2_larger:
ADD R1, R2, #0 ; store R2 in R1
BRnzp done ; go to done
equal:
AND R1, R1, #0 ; store 0 in R1
BRnzp done ; go to done
done:
HALT
Here's how the program works:
Initialize R1 to 0.
Subtract 1 from R2 and R3 and store the result in R4 and R5, respectively. This is necessary because the LC-3 does not have a subtract instruction, so we have to add the two's complement of the second operand to the first operand to simulate subtraction.
Check if both R2 and R3 are positive. If they are, go to the both_positive label.
If R2 is negative, go to the R2_negative label.
If R3 is negative, go to the R3_negative label.
If both R2 and R3 are positive, subtract R3 from R2 and check the result to determine which number is larger.
If R2 is negative, add the two's complement of R2 to R3 and check the result to determine which number is larger.
If R3 is negative, add the two's complement of R3 to R2 and check the result to determine which number is larger.
Store the larger number in R1.
If the numbers are equal, store 0 in R1.
Halt the program.
Note that this program assumes that the numbers in R2 and R3 are signed 16-bit integers in two's complement format. If the numbers are unsigned, the program would need to be modified accordingly.
SPJ11