Error question

[LinearChaos]

I have a question: Why would the first 4 digits for M=D by 1110, instead of 1111, since M=D is an M instruction?

[WBahn]

How is the computation mnemonic "D" an M instruction???

The fourth bit dictates whether the A register or the M register is fed to the Y-input of the ALU. Since the computation in M=D is simply D, it doesn't matter whether your instruction uses the A or the M.

[LinearChaos]

Ah, yes! Thank you so much!

I've finished my Hack Assembler now (I used C++) and it's successfully completed all of the comparison tests! Phew!