Observe the Emory Honor Code when doing homeworks.

1. Purpose

This is your first assembler programming assignment and it is very easy to do. The difficulty of this assignment is: learning the EGTAPI programming environment.

The purpose of this homework is primarily to allow you to get used to the EGTAPI (Emory Graphical Tool for Assembler Programming Instruction) system before the serious project assignments are given, and introduce you to the EGTAPI programming environment.

The tutorial of the Emory Graphical Tool for Assembler Programming Instruction (EGTAPI) can be found here:

Documentation for Egtapi: click here .

I have used Egtapi in class and explained how to work with it. You should be able to use Egtapi without reading through the complete documentation. But browse the content of the documentation so you get familiar with the topics and can consult the documentation if you need to find some feature that you need to use.

2. Install EGTAPI on your laptop (you should have done this already...)

• If you have not yet done so, download and install EGTAPI from the following URL:

  http://www.cs.emory.edu/~egtapi/download.html

  After downloading the file, you must create a directory called (say) cs255 and extract the downloaded compressed archive into this cs255 directory in your laptop.

• After you have extracted the files, open a file browser and go into the cs255 folder.

  Click on the Egtapi icon to start EGTAPI.

3. Preparation

• To do this project, you must obtain a copy of the prepared files with EGTAPI

  Use project code hw8

  You will have create a hw8 folder containing these program files:

  hw8.s Assembler program file for this homework assignment

4. The Skeleton Project File "hw8.s"

The assignment consists of 10 easy questions given inside the assembler program hw8,s that was copied into your project directory through the preparation step above.

You must edit the project file "hw8.s" and write the required assembler instructions in this program file.

How to edit the project file hw8.s file:

Although Egtapi has an edit function, I recommend you use ssh to remote login to a labmachine and edit hw8.s with the nano editor. If you insists on using Egtapi's editor, you should save your work frequently - because Egtapi can time out and the edit window will freeze (you will lose your work). Read this write up about Egtapi's editor: click here

The skeletal program has 10 sections, labeled as Q1, Q2, ..., Q10 where you put assembler instructions

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• Advice:

  Do the project piece meal: Write the assembler instructions for question 1 at label Q1 Then compile and run the program hw8.s When Q1 is done, do Q2, and so on When you test the assembler instructions for a question, use the STEP button (for explanation of the menu buttons, see this webpage: click here ) When you want to skip over an already tested section of the project, use the RUN button --- it will skip to the code of next question (for explanation of breakpoint, see this webpage: click here )

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• Assignment:

  These instructions on how to do the assignment is given inside hw8.s Basically, you must write the assembler instructions to execute a given assignment statement in each section marked with the labels Q1, Q2, ..., Q10 in the hw8.s file.

  Recall from the lecture(s) that:

  Byte type variables are one byte in length, Short type variables are two bytes, and Integer type variables are 4 bytes long.

  Warning:

  Be very careful and use the correct operand size in each assembler instruction. In other words: be careful when you load a value, make sure you used the correct ldr instruction: Use ldrsb when you load a byte value Use ldrsh when you load a short value Use ldr when you load a int value And be careful when you store a value, make sure you used the correct str instruction: Use strb when you store a byte value Use strh when you store a short value Use str when you store a int value

  There are some more helpful hints on testing your program in the next section !!!

5. Running/testing the program

The main purpose of this assignment is to get you familiarized with the Egtapi environment. So follow the following instruction carefully.

This is how you run your program "hw8.s":

1. Edit your assignment program (hw8.s) according to the instructions above...

   You can complete 1 question at a time and compile and test the program.

2. After you're have finished writing some part of the assembler program, you can compile the program as follows:

   First, assembler the program using EGTAPI. Read this webpage on how to assembler an assembler program that consists of a single file: http://www.cs.emory.edu/~cheung/Courses/255/Egtapi/Docs/doc2019/compile.html It's very easy: Open the File Browser tab in Egtapi Select hw8.s Click on Compile. The compile window will pop up. Click compile in this window. When the compilation is successfully, you will see this message: Compiled successfully Please refresh the file browser. If you do not see Compiled successfully, the right window will contain the error messages. The left window contains the program listing with line numbers. You must edit the program and recompile until it compiles successfully before you can run it ! If successful, you will find the executable code in hw8.arm To run the program in Egtapi, you selecting it and then click Load and then use the program control buttons in Egtapi to execute the program. See next section on how to run the program. The program compilation will also generate a listing file hw8.list and an error file hw8.error. These files are not used in the program execution. The listing file does contain interesting information about the placement of the variables in the memory (symbol table) -- which can be enlightening

3. Loading your assembler program for execution:

   If compilation is successful, you can load the executable file hw8.arm in EGTAPI http://www.cs.emory.edu/~cheung/Courses/255/Egtapi/Docs/doc2019/load.html Basically, you select hw8.arm and click Select. If all is well, the program will stop at the breakpoint main. You will see this in the Breakpoint window: The label main is highlighted - indicating the program has stopped at the label main You will see the first instruction in your program in the Curr. Instr window. Now you are ready to run your program.

4. To run your program, use the program control panel:

   In this assignment, you should only use the Step key and the Run key.

   The Step key (right arrow with a bar):

   The Step will cause EGTAPI to execute the current assembler instruction and stop.

   You can experiemnt with the Step to execute code for Question 1 of the assignment (after you have written it).

   If your code is correct, after pressing about 4 - 5 Step, you will see the variable ans_s change from ans_s = 0 to ans_s = 44 in the variable window EGTAPI:

   The Run key will run the program and program execution will only stop when it reaches a breakpoint.

   I have already set up 10 breakpoints in the program and they are shown in the break point panel in Egtapi:

   These label have been defined in hw8.s and corresponds to questions in the assignment.

5. How to check for errors:

   Press the Step button repeatedly (but SLOWLY !) to check the execution of your program. While you are pressing the Step button, look at how the variables ans_b, ans_s and ans_i variables - specifically, look for the correct values moved in these variables in the "Variable Watch" window. Make sure the values are right (according to the questions in the project assignment).

6. Program end:

   EGTAPI will stop when it reaches the instruction at the Stop label. When EGTAPI reaches the Stop label, the Step (and other buttons) will no longer work. If you want to re-run the program, you can click on Reload. If your program is complete and correct, you can turn in the project.

7. If you found an error (i.e.: you detects that the value stored in some variable is incorrect), then you must correct your error:

   Edit your hw8.s file (Use EGTAPI, File Browser, select hw8.s and click Edit) Compile the program after you finish editing (and saving the file) (Click File Browser, select hw8.s and click Compile) Re-run the program. (Click Reload)

   If you discover more errors, just repeat the above steps until your program is error-free.

6. Turn in

Turn in your hw8.s program using Egtapi using turnin code hw8

7. Extension request

• Request an extenion for this assignment with Egtapi using assignment code hw8 before the due date