Question

In LC3, Multiply whatever is in R0 by 6, and store it in R1

For ex, if R0 has 5, R1 will contain 30

Answer 1

Below is the LC3 code to do this

AND R1, R1, 0 //R1 will store value 0 now

AND R2, R2, 0 //R2 will store value 0 now

ADD R2, R2, 6 //R2 will store value 6 now

ADD R3, PC, 2 //Store value of PC+2 into R3 which is the value of next instruction with label START

START :- ADD R1, R1, R0 //R1 = R1+R0

ADD R2, R2, -1 //This will reduce the count of R2 by 1

BRz END //Branch to label END if R2 becomes 0

JMP R3 //Jump at label START which is stored in R3, if R2 is not zero

END :- RET //Return instruction

In the above instruction R2 initially holds value 6 and acts as counter. We repeatedly add R0 with R1.

Please comment for any clarification.