Re: ALU - Don't know where to start

Posted by cadet1620 on Feb 13, 2013; 6:17pm
URL: http://nand2tetris-questions-and-answers-forum.52.s1.nabble.com/ALU-Don-t-know-where-to-start-tp4026279p4026285.html

Technik wrote

What exactly are ng and zr and what purpose do they serve? The rest make sense (zx = zero X; ny = negate y, etc) but I'm not sure I understand what the "status" bits are.

The status bits give information about the numerical value of the ALU's output. If the output is 0, then zr is true. If the output is a negative number, then ng is true. If the output is a positive number, both status bits are false.

The status bits will be used in project 5 to implement conditional jumps in the CPU.

--Mark