# CPSC 213: Assignment 1 solved

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## Description

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Goal
The goals of this assignment are for you to get some of the preliminary stuff under your belt:
• get comfortable with hex, integers, and endianness
• familiarize yourself with the Unix command line
• write, compile and run a very simple C program
• understanding endianness and how to detect it using a program
• install the SimpleMachine simulator on your machine
• implement the MainMemory class used by the SimpleMachine simulator.
Part I – Endianness and Hex Questions
The table below lists the content of memory between address 0x7000 and 0x70FF. Every
number is shown in hex. For example the value of the byte at address 0x7058 is 0x15.
1. What is the value (in hex) of the little-endian 4-byte integer stored at location 0x7064?
2. What is the value (in hex) of the big-endian 4-byte integer stored at location 0x7048?
3. What is the value (in hex) of the big-endian 8-byte long long stored at location 0x7090?
4. At what address is stored the 4-byte little-endian integer 0x609070A4?
5. Give an example of a 4-byte integer whose big- and little-endian representations are
identical. Can you generalize this example?
6. Consider a hypothetical situation in which two different processors (possibly made by
different manufactures) are accessing the same memory. The first processor computes “1
+ 65536” and stores this in memory at location X. Then the second processor reads the
value at location X and adds 1 to it, only to discover that this value is actually 16777473,
not 65538, as expected. What has gone wrong? HINT: Start by converting the base-10
numbers involved into hex. Use a calculator or the computer (e.g., printf (“0x%x
\n”,i); prints the value of i in hex preceded by “0x”).
Part II — Install the Simple Machine
contains two jar files and two zip files.
• SimpleMachine213.jar
A reference implementation of the SM213 simulator with classes obfuscated so that you
can’t decompile them to see the implementations of MainMemory.java and CPU.java,
which are the classes that you will implement over the next several assignments.
Type java -jar SimpleMachine213.jar at the Unix command line to run the
reference implementation.
• SimpleMachineStudent.jar
Contains the “student” version of the simulator that has only stubs for MainMemory.java
and CPU.java.
• SimpleMachineStudentDoc213.zip
• SimpleMachineStudentSrc.zip
Source for the student version.
Most of you will use Eclipse as your IDE for the course. If you will, also download the file
Follow the instructions in Appendix B of the Companion to install the Simulator into Eclipse (or
if you prefer, another IDE). If you are using Eclipse, then the simplest instructions are in
Section~B.1.
Most of this is just preparation for next week when we start to use the Simulator. But, there is
one thing to do for this assignment once you have installed the simulator.
Part III — Implement the Memory class.
Like a real machine, the simulator has a Memory and a CPU. You are going to build both of
them. This week, the Memory.
The MainMemory class is in the package arch.sm213.machine.student. This class
simulates main memory by storing its content in an array of bytes. That part is already done for
you. You must implement the five methods flagged with “TODO” comments.
Create a set of JUnit tests to test your implementation in the class MainMemoryTests in the same
package. Do not worry about running the simulator itself just yet. Just get your unit tests to
pass. Comment each test to explain what it is testing and to demonstrate test coverage.
Part IV – A Simple C Program
Unix Development
Much of the programming you will do in this course will be in Java using Eclipse or in assembly
language using the Simulator. But, for some of what you will do you will need a Unix
development environment. One of the requirements of this first assignment is that you get a
Unix environment setup and become familiar with it. You have some choices.
You can use the departmental machines, if you like. You can access these machines remotely
If you want to use a Windows machine you need to install Cygwin (Microsoft’s C Visual Studio
environment and their C development tools will not work for this class). Cygwin provides your
Windows machine with a Unix command line and various development tools. Be sure to specify
that you want “gcc” included when you install it.
If you want to use a Mac you need to install Apple’s Development Tools (Xcode and related
command line tools). This is an optional instal that is available as a free download from Apple
https://developer.apple.com/xcode/.
C and Endianness
In class I gave you the outline of a C program that casts an int into an array of bytes. Modify
this program (or start from scratch) to create a program that prints “Big Endian” on big-endian
architectures and “Little Endian” on little-endian architectures. Name this program
“endian.c”
Test this program by running it on at least two different processors —- Sparc and Intel x86 —-
running Unix-like operating systems (e.g., Mac OS, Linux, SunOS etc). Intel x86 machines are
easy to find. Sparc machines are a little harder (galiano.ugrad.cs.ubc.ca is one). You can use the
“uname” command shown below to determine a machine’s type. You need to recompile your
program for each machine you try.
gcc -o endian endian.c
If you do this, then you run your program by typing:
./endian
Part of the goal here is to get comfortable with the UNIX command line, for editing, compiling
and running C programs etc. by starting with a simple example. Here are some useful commands.
What to hand in AND HOW
You must use a program called handin to hand in your assignments in this course. To use this
program you need a CS account. If you don’t have one you must get one. Its easy. Here’s a
There are two ways to use handin: from the UNIX command line or from the Web.
You will find the instructions for using the command line version of handin here: https://
my.cs.ubc.ca/docs/handin-instructions (that page tells you everything you need to know, but note
that the page currently has a bug: you don’t type man handin at the command-line prompt to
get a description of how to run the program, you simply type handin).
You will find the instructions for using the web version here: https://my.cs.ubc.ca/docs/hand-in.
command purpose
uname -a display the ISA and other characteristics of the current system
emacs a text editor for writing source code (Eclipse will work too)
gcc compile a program into an executable
man display the manual page (documentation) for a unix command
gdb the gnu symbolic debugger (for debugging C programs)
Whichever one you use, please double check that it worked correctly;
the instructions show you how. We will not accept homework
submitted any other way (e.g., email).
Use the handin program to hand in the following:
1. A single file called “README.txt” that includes your name, student number, four-digit
cs-department undergraduate id (e.g., the one that’s something like a0b1), and all written
material required by the assignment as listed below.
3. The C program you write as a separate file called “endian.c”.
4. A list of the machines on which you ran your C program and what it said about their
Endianness. For each of these machines, use the uname program to determine the ISA of
the machine and include this in your report. Include this in the README file.
5. Your implementation of the arch.sm213.machine.student.MainMemory and
your JUnit test class. Include only two java files: MainMemory.java and
MainMemoryTests.java. Do not include any other java files or any class files. Do
not include any directories or sub directories.
6. A description of the results of your testing. If your test cases provide full coverage and
all tests passed, it is sufficient to just say this. But, if certain things do not work, you
must indicate this. Include this in the README file.
The handin assignment directory name for this assignment is a1.