Assembler Changing Code

[cjm4443]

I'm attempting to run something I've assembled in the Assembler on the CPUEmulator. However, when I have the command "D = D + 1", the Assembler turns it into "D = D<A". I think it's what's messing up my program and I don't understand why this is happening.

[ivant]

First of all, you should not treat the Assembly instructions like D=D+1 as expressions. That is "D=D+1" is the name of the instruction, whereas "D = D + 1" is an error, because it has spaces.

Second, there is no "D=D<A" instruction. I'm perplexed where this can come from.

I suggest that you read Mark's Introduction to Hack Assembly Language: http://nand2tetris-questions-and-answers-forum.32033.n3.nabble.com/Introduction-to-Hack-Assembly-Language-td4032232.html

(Strange, the forum software seems to have bugged. It doesn't show quotes, links, and other markup properly,)

[WBahn]

Which assembler? The one that you wrote?

What, exactly, do you mean by the assember is turning the command D = D + 1 into D = D<A? Where is it, exactly, that you are seeing the "D<A" appear?

[WBahn]

ivant wrote

First of all, you should not treat the Assembly instructions like D=D+1 as expressions. That is "D=D+1" is the name of the instruction, whereas "D = D + 1" is an error, because it has spaces.

The Hack Assembly Language spec allows the spaces, since it explicitly states that spaces are ignored. So a conforming assembler should assemble this just as if it had been "D=D+1".

[ivant]

WBahn wrote

The Hack Assembly Language spec allows the spaces, since it explicitly states that spaces are ignored. So a conforming assembler should assemble this just as if it had been "D=D+1".

WOW. I always thought of this as the white space around the command not. But you are right, the assembler does allow it.