LS-3 ASM

Question 1

Create a simple program that loads data into register one, perform a bit-wise not operation and store that in result.

Answer 1

Question 2

Each non blank line in lc-3 is what?

Answer 2

• An instruction (ld r1, data)
• An assembler directive (.orig x3000)
• A comment

Question 3

What is the typical form an instruction has in LC-3?

Answer 3

Label OpCode Operands ;Comments

Question 4

What does an instruction consis of?

Answer 4

An opcode and one or more operands

Question 5

What are opcodes?

Answer 5

Question 6

What does Operands do? And what are typical operands?

Answer 6

Question 7

Line by line, what does the following code do?

Answer 7

Question 8

How would you load data into register 1?

Answer 8

ld R1, data

Question 9

How do you store the contents of register 3 into result?

Answer 9

st R3, result

Question 10

What can you think of labels as?

Answer 10

They are a symbolis name for a memory location (the line is usually denoted by a hex value)

Question 11

How do Assembler Directives work?

What are the Assembler Directives/What do they do

Answer 11

Question 12

In general what are traps?

Answer 12

Question 13

What are the traps and what do they do?

Answer 13

Question 14

In general how does the Assembly process work?

Answer 14

Question 15

What happens during the first pass of the assembly process

Answer 15

Question 16

What happens during the second pass of the assembly process

Answer 16

Each line scanned again

Everything translated into machine languge

Does using the symbol tables, fillng in labels like a macro.

Fill memory loctions as directed by assembly directives

Question 17

In general what is Linking and Loading?

Answer 17

Question 18

What are the output files the Assembler generates?

Answer 18

Question 19

How do you read in a character and how do you print that character to console?

Answer 19

Question 20

How do you print a string to console?

Answer 20

Question 21

In general, what is a condition code?

Answer 21

There is a process to determine based on the last arithmatic/logic expression if the result was zero, poisitive or negative.

Question 22

What are the instructions that affect the condition code?

Answer 22

Question 23

What is the condition code after each line of code?

Answer 23

Question 24

How does conditional branching work?

Answer 24

Question 25

Create a simple loop that loops 10 times

Answer 25

Question 26

What are the 7 forms of branching and when do they work?

Answer 26

Question 27

Provide the code for a simple if statement that checks if R1 is positive after an add instruction, If it is, it executes code starting from label if. Otherewise it branches to label skip

Answer 27

Question 28

Provide an example of an If-Else Statement

Answer 28

Question 29

Create a while loop that reads a chracter and prints it 10 times using a loop

Answer 29

Question 30

Create a while loop that iterates through the numbers from 1 to 100 and summ all the odd numbers and store result in register r2

Answer 30

Question 31

When branching what is the limitation for distance from PC counter?

Answer 31

Must be within -255 and 256 words of the BR instruction (because we only have 9 bits to hold the offset)

Question 32

What is the symtax for an unconditional branch?

Answer 32

Question 33

How do you overcome the limitation of distance from pc relative?

Answer 33

Using LEA, one can store in the register the address (pointer) of the next instruction.

Example:

br loop (loop label needs to be -255 to 256 of the br intruction

loop

LEA r4, EXIT

jmp (or br) r4

can jump anywhere in memory space