This assignment asks you to implement a simple terminal calculator in assembly.

You may work on Github Codespaces, or use our Docker container. You can also work on Khoury Login. We will assume that the submitted code was tested on one of these platforms.

Task

Your task is to complete the main function (under the label main) in calculator.s so that it implements the following functionality:

1. The calculator can be invoked on the command line as follows:

   $ ./calculator

2. After launching, the calculator will accept a line of input in the following format:

   $ <integer1> <operation> <integer2>

   The four valid operations are:

   • +: add
   • -: subtract
   • *: multiply
   • /: divide

3. You may assume that the line will always contain a valid integer, a single character, followed by a valid integer.

4. When the input consists of 2 valid signed long integers with a valid operation in between, the result of the corresponding operation should be printed to the terminal. An error message should be printed if the operation cannot be performed, that is, when it would result in an operating system exception. There should be only one line of output and that line should only contain a single long integer or an error message.

   A sample interaction should be as follows:

   $ ./calculator
   50 - 51
   -1

5. If the operation is invalid (i.e., not one of +, -, *, or /), the error message should be Unknown operation. Other error messages are up to you. You do not have to handle overflow, but you should handle division by zero.

6. The main function shall return 0 on success and 1 if there was an error.

Here are a few more examples of running your program:

$ ./calculator
12 + 43
55
$ ./calculator
33*78
2574
$ ./calculator
3 / 11
0
$ ./calculator 
57 ^ 3
Unknown operation

Using scanf

The most convenient way to read input for our simple example, is to use the scanf function from the C library. Follow the class example posted on Piazza. The starter code already contains labelled “slots” for the two integers and a character. You just need to pass them to scanf and use their contents after it returns. Make sure you understand when to put $ in front of a label.

We recommend experimenting with scanf by writing a very simple C program.

Do not be afraid to ask questions.

Code Layout

When writing assembly, follow these simple rules:

1. Labels, .global, .text, and .data are aligned on the left edge.
2. Instructions and data definition directives are indented by 2, 4, or 8 spaces (pick one and be consistent)
3. Think of groups of instructions as logically corresponding to an individual higher level operations, e.g., calling a function entails loading argument registers and the call instruction itself. Separate logical groups by empty lines. Add comments to indicate your intent (e.g., “Add left-hand side and right-hand site, storing the result in rax”).

Using the Makefile

We have provided a very basic Makefile for you. You can compile your program simply by running make on the command line. Running make clean should help you prepare your working directory for committing to git and for submission. Read the comments in the makefile and look at this tutorial if you have questions: https://makefiletutorial.com/.

Deliverables

• Modify the file calculator.s and commit it to your repository.

• Do not include any executables, object files, or any other binary, intermediate or hidden files. That means, e.g., no .o files, no files or directories starting with . (like .git), etc.

• Finally, download a ZIP archive of your repository (available on Github) and submit it to our Gradescope.