private void doInput(String[] arguments) {
    if (arguments.length < 2) {
      printError("-i : No filename specified");
    }

    if (arguments[1].endsWith(".pco")) {
      machineCode = true;
      assembler = new MachineCodeAssembler();
    } else {
      if (!new File(arguments[1]).exists()) {
        print("...no file extension specified.  Guessing .pca");

        arguments[1] = arguments[1] + ".pca";
      }
    }

    try {
      sourceFile = SourceFile.load(arguments[1]);
      baseFileName = arguments[1].substring(0, arguments[1].lastIndexOf("."));
    } catch (IOException e) {
      printError(e.getMessage());
    }
  }