Shall we deal with the error input?

[woodylcy]

I mean we guarantee  that the input .asm file is right?

   I know someone has asked this kind of question, but I think my program is so awkward.
And there are instructions like this: D+A  A+1   ...   , when we write the .asm program, will A+D 1+A  ... do?

thanks very much. I am just a beginner with little programming experience

[cadet1620]

You should check that the input is valid, and print an error message and abort.

The easiest way to write Code.comp is to write a table of comp strings and their instruction bit values. For example, in my assembler (written in Python) I have:

_compDict = {
    ...
    'D+1': '0011111',
    'A+1': '0110111',
    ...
    'D+A': '0000010',
    'A+D': '0000010',
    ...
};

Most high level languages have an easy way to search a table like this. If the mnemonic is not found, print an error message and abort. Otherwise, return the bit string.

You can see that I chose to support D+A and A+D, but not 1+D or 1+A. It would be simple to add them to the table if in the future I want to support them.

--Mark