Lab 4: Roman Numeral Conversion

Lab 4: Roman Numeral Conversion
Lab Objective
In this lab, you will develop a more detailed understanding of how data is
represented, stored, and manipulated at the processor level. In addition to
strengthening your understanding of MIPS coding, you will use program arguments to
read a string input and learn how to convert Roman numerals into binary and how to
print digits as ASCII characters.
Lab Preparation
1. Read sections 6.4, 9.2 - 9.3 from Introduction To MIPS Assembly Language
Programming.
2. Learn how to interpret Roman numerals here
Specification
You will write a program in the MIPS32 language using the MARS integrated development
environment to convert a Roman numeral input into an integer. You will then print the
integer as a binary ASCII string.
Input
You will be using program arguments instead of a syscall to take user inputs. See
this document on how to use program arguments.
Sample Outputs
Valid Inputs
You entered the Roman numerals:
XXVI
The binary representation is:
0b11010
-- program is finished running --
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You entered the Roman numerals:
CXCIX
The binary representation is:
0b11000111
-- program is finished running --
You entered the Roman numerals:
CCCLXXXVIII
The binary representation is:
0b110000100
-- program is finished running --
Non Valid Inputs
You entered the Roman numerals:
CIC
Error: Invalid program argument.
-- program is finished running --
You entered the Roman numerals:
IIIV
Error: Invalid program argument.
-- program is finished running --
You entered the Roman numerals:
V111
Error: Invalid program argument.
-- program is finished running --
Extra Credit
In this example, the input is non-minimal, so it is counted as a non valid input.
You entered the Roman numerals:
VIIII
Error: Invalid program argument.
-- program is finished running --
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You entered the Roman numerals:
DCXXIV
The binary representation is:
0b1001110000
-- program is finished running --
For full credit, the output should match this format exactly. Take
note of the:
1. Exact wording of the statements.
2. Program argument printed on a new line.
3. Blank line under the program argument.
4. Binary value printed on a new line.
5. Blank line under the final result or invalid program argument error.
Functionality
The functionality of your program will be as follows:
1. Read a Roman numeral input from the program arguments.
● Valid ASCII characters are I, V, X, L, and C
● Assume program argument input will have a max of 20 characters
2. Print the user’s input.
3. Convert the Roman numeral input to an integer and store in $s0.
● Your program should parse through the ASCII string and compare adjacent
characters to decide if you must add or subtract or if the input is
invalid.
● Basic conversion algorithm:
i. Iterate over each character of the string
1. Compare value of the current character to the value of the
next character
a. If current value is greater or equal, add value to
running sum
b. Else, subtract value from running total
4. Print an ERROR message if:
● The user entered invalid ASCII characters
● An invalid Roman numeral string has been entered
5. Exit the program cleanly using syscall 10.
6. Extra credit options
● Include D as a valid input from the user
● Print error message for non-minimal Roman numeral input
Part A: Block Diagram, Pseudocode, and Program Arguments
In part A, you must create a block diagram and pseudocode to aid in the development
of your MIPS assembly program. In addition, you must generate code to print the
program argument to the console.
Block Diagram
Before coding, create a top level block diagram or flowchart to show how the
different portions of your program will work together. Start by creating a flow chart
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of the steps that were previously described. Next, break each step into its own block
diagram.
Use https://www.draw.io or a similar drafting program to create this document. This
diagram will be contained in the file Diagram.pdf. This diagram must be
computer generated to receive full credit.
Pseudocode
Next, you will create pseudocode that outlines your program. Your pseudocode will
appear underneath the header comment in Lab4.asm. Guidelines on developing pseudocode
can be found here: https://www.geeksforgeeks.org/how-to-write-a-pseudo-code/
You may modify your pseudocode as you develop your program. Your pseudocode
must also be present in your final submission (part B).
Program Arguments
Your code must read and print the program argument to the screen. For example:
Input
Output
You entered the Roman numerals:
XXVI
-- program is finished running --
Part B: Assembly Code
Implement the functionality of the program previously listed.
Automation
Note that part of our grading script is automated, so it is imperative that
your program’s output matches the specification exactly. Output
that deviates from the spec will cause point deduction.
Your code should end cleanly without error. Make sure to use the exit
syscall (syscall 10).
Files
Diagram.pdf
This file will contain a block diagram or flowchart of how the different components
of your code work together.
Lab4.asm
This file contains your pseudocode and assembly code. Follow the code documentation
guidelines here.
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README.txt
This file must be a plain text (.txt) file. It should contain your first and last
name (as it appears on Canvas) and your CruzID. Your answers to the questions should
total at least 150 words. Your README should adhere to the following template:
------------------------
Lab 4: Roman Numeral Conversion
CMPE 012 Spring 2019
Last Name, First Name
CruzID
-------------------------
Can you validly represent the decimal value 1098 with Roman numerals using
only I, V, X, and C?
Write the answer here.
What was your approach for recognizing an invalid program argument?
Write the answer here.
What did you learn in this lab?
Write the answer here.
Did you encounter any issues? Were there parts of this lab you found
enjoyable?
Write the answer here.
How would you redesign this lab to make it better?
Write the answer here.
What resources did you use to complete this lab?
Write the answer here.
Did you work with anyone on the labs? Describe the level of collaboration.
Write the answer here.
Syscalls
When printing the integer values, you may use syscall system services 4 (print
string) and 11 (print character). You may not use the following
syscalls:
1 (print integer)
5 (read integer)
12 (read character)
34 (print integer as hexadecimal)
35 (print integer as binary)
36 (print integer as unsigned)
You will lose a significant number of points if you use any of these syscalls. See
the rubric for more details.
Make sure to exit your program cleanly using syscall 10.
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Note
It is important that you do not hard-code the values for any of the
addresses in your program.
Other Requirements
Turn Off Delayed Branching
From the settings menu, make sure Delayed branching is unchecked
Checking this option will insert a “delay slot” which makes the next instruction
after a branch execute, no matter the outcome of the branch. To avoid having your
program behave in unpredictable ways, make sure Delayed branching is turned off. In
addition, add a NOP instruction after each branch instruction. The NOP instruction
guarantees that your program will function properly even if you forgot to turn off
delayed branching. For example:
LI $t1 2
LOOP: NOP
ADDI $t0 $t0 1
BLT $t0 $t1 LOOP
NOP # nop added after the branch instruction
ADD $t3 $t5 $t6
MIPS Memory Configuration
To find the program arguments more easily in memory, you may choose to develop your
program using a compact memory configuration (Settings -> Memory Configuration).
However, your program MUST function properly using the Default memory
configuration. You should not run into issues as long as you do not hard-code
any memory addresses in your program. Make sure to test your program
thoroughly using the Default memory configuration.
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Submission Instructions
This assignment will be submitted in two parts. Late hours will not be used for Part
A of the assignment. If you do not submit a diagram or pseudocode by the Part A
deadline, you can submit it with your Part B submission for less points.
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Grading Rubric
point values to be determined
Part A
pseudocode
block diagram
program arguments
Part B
pseudocode quality
block diagram quality
assembles without errors
correct value in $s0
statements match specification
invalid input detection
test cases
extra credit
-50% if program only runs in a specific memory configuration or memory addresses are
hard coded
-25% incorrect naming convention
No credit if you use a forbidden syscall (1, 5, 12, 34, 35, 36)
6 pt style and documentation
1 pt comment on register usage
1 pt useful and sufficient comments
1 pt labels, instructions, operands, comments lined up in columns
2 pt readme file complete (should total at least 150 words)
1 pt complete headers for code and README
Note: program header must include name, CruzID, date, lab name,
course name, quarter, school, program description, note on
program argument usage
README must include name, CruzID, lab name, course name
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