Goals

  • Learn about error-correcting codes.

  • Learn to program in the TOY machine language.

  • Appreciate the programming and debugging advantages of a structured programming language over machine language!

    • TOY simulators

    To run your program, you will want to use one of the following TOY simulators. We'll grade your programs using the C TOY Simulator but it may be more convenient to develop your code with the Visual X-TOY simulator.

  • The TOY simulator in C from lecture is available at /u/cs126/files/hamming/. To use the simulator, do the following:

  • Compile the simulator with: 
    Unix:         % gcc126 toy.c -o toy
Windows:   C:\> lcc126 toy.c
    Test it by typing: 
    % toy multiply.toy
    The TOY program expects you to enter two integers from stdin. It outputs their product to stdout.

  • The Visual X-TOY simulator from lecture provides lots of useful development features.

    • Checking your work and hints

  • The most complete way to test your TOY programs is to encode and decode all possible inputs. Use the files all4.txt and all4.txt.ans to debug encode.toy: the first file contains all possible 4-bit inputs, the second contains the desired output. Use the files all7.txt and all7.txt.ans to debug correct.toy: the first file contains all possible 7-bit inputs, the second contains the desired output.

  • If you are using the Java X-TOY simulator, you can use Mode -> Load File to Stdin to redirect stdin from a file. If you are using the C simulator, you can use the following command: 
    toy encode.toy < all4.txt

  • As a special bonus, we provide reference implementations in C: encode.c and correct.c.

    • Debugging Hints

    Here are some debugging hints that may help you out.

  • Remember that all values, "line numbers", and arithmetic are in hex. This is by far the most common error. For example, 1A comes after 19.

  • Comment your TOY code. Also, this may sound silly, but don't accidentally update your comments and forget to update the actual code!

  • All registers are global variables, so be careful.

  • Watch out for jump statements - if you insert a new line of code between existing lines, the location that you want to jump to may change.

    • Submission and readme

  • Submit the following files: 
    readme.txt encode.toy correct.toy
    Do not use different file names.

  • Comment your encode.toy and correct.toy programs.

  • The readme.txt file should contain the following information. Here is a readme template.

  • Name, precept number.

  • High level description of code, any serious problems you encountered, and whatever outside help that you received.

  • For each program, include a table indicating what each of the registers are used for.

  • Indicate whether you used the C or Java TOY simulator to develop your code.


    • Kevin Wayne