Programming Wombat in Assembly

• Setup
  • I have installed a copy of executable on the department systems.
    • You will need to have gui access (In the lab on a linux machine) for the GUI simulator.
    • You will need terminal access for the text based simulator and for the assembler.
  • While you can run the applications with the full path from the command line, you probably want to add them to your environment.
    • In your home directory edit the file .bashrc
    • Add the following line
    • export PATH=$PATH:~dbennett/wombat/bin
    • After you save the file, type the following at the command line
    • . .bashrc
    • You will not need to do this again.
    • This will add my wombat/bin directory to your search path.
    • These executables will probably not run on cslab100 or 101.
• Writing a program
  • write a program in assembly language, using an editor, in a file.
  • We will discuss this next.

  • # foo.a
    read 
    store  100
    read 
    store  102
    add    100
    store  104
    load   100
    write 
    load   102
    write
    load   104
    write
    stop
    	

  • Compile the program

    • $ was foo.a
      	

    • This will either "assemble", which means it produces no errors and the output file a.out
    • Or it will fail with error messages.
    • If your editor does not add a newline to the last line of the file, you will receive an error. Sorry, I need to fix this.
  • If it "assembled", run it
    • A text based simulator sim a.out will just run the program.
    • A GUI based simulator guiSim a.out will open the program in a visual environment.
• Some was options
  • You can rename the output file from was with the -o option, just like C/C++
  • -t will show the symbol table (if there is one)
  • -v will prodcue a verbose output.
• Programming in WOMBAT assembly language.
• general instructions:
  • mnemonic
  • mnemonic address
  • mnemonic label
  • The last is the most interesting. was will resolve labels if they are properly formed.
    • This makes it MUCH easier to code.
    • Labels can be for data or code
    • Labels care declared before code or assembly directive.
    • Start with letter, contain only letter, digit underscore.
    • Must not be a reserved word.
  • Data is declared with the .data directive.
    • The size in bytes is given (don't use an odd number)
    • The default value is given.
    • varName: .data 2 100
• comments start with a ;
• Write a program that adds prints the numbers 1 to 10
• Write a program that reads in a lower limit and an upper limit and prints the even numbers between these two limits.