Eval button unavailable

[97vyaas]

I was unable to find Xor.hdl in my 00 projects file for first assignment (as described in the video). I typed in the following code on the Xor.hdl file in 01 file under projects:

CHIP Xor {
    IN a, b;
    OUT out;

    PARTS:
    // Put your code here:
    Not (in=a, out=nota);
    Not (in=b, out=notb);
    And (a=a, b=notb, out=c);
    And (a=nota, b=b, out=d);
    Or (a=c, b=d, out=out);
}

After I changed one of the variables to 1 or 0, the eval button remains unavailable. But when I use the built-in Xor.hdl chip, it works properly. Can anyone help me with this? Thanks!

[WBahn]

Do that directory have the original Not, Or, and And .hdl files in it? If so, the simulator is trying to use those files for those gates and since they are empty it can't run. Simply move or rename those files to something else. That will force the simulator to use the builtin chips.

[97vyaas]

That worked! Thanks  a lot for the quick response.

[dougboari]

Thank you so much! I was pulling my hair out and I don’t have that much hair to spare!

[apfcheng]

Meanwhile, I find that there is another subfolder called "demo" under folder "projects"
I use the Xor.hdl in there, and it works, the Evaluate button appears as expected.