# Machine language

###### tags: `computerArchitecture` `machineLanguage`

https://www.youtube.com/watch?v=lavxkeFlRI4&list=PLu6SHDdOToSdD4-c9nZX2Qu3ZXnNFocOH&index=10

We create the logic gate build sequential circuits and even construct an ALU an arithmetic logic unit, but put those together in the useful way. We need to understand how we're going to communicate our intention to our CPU through the machine code.

## Addhack

This is going to add two numbers together.

Now, we have to disassemble it by hand into hack assemble code

0000000000000010
1110110000010000
0000000000000011
1110000010010000
0000000000000000
1110001100001000

the most significant bit of each instruction tells us if it is an A instruction or a C instruction

An a instruction just say put this number to in the a register.


The first instruction here begins with a 0 which means it's an A instruction

---

C Instruction


>Bit 2 and bit 3 are unused bit

>Bit 4 indicate whether the alu will treat the a register as a direct register or an index in the memory

>Bit 5 through 10 are used tell the ALU what computation to do

>bit 11~13 indicate what combinations of the A,M and d registers the result of the operation is to be stored in

>bit 14~16 tell the CPU under what conditions it should jump. that is change the program counter to a new destination

More deep here
the bit(0101) 11~13 is tell the cup D register is the destination

and bit 4 ~ 10(0110000)tell the ALU to emit a register value

0000000000000010 //@2
1110110000010000 //D=A
0000000000000011 //@=3
1110000010010000 //D=D+A
0000000000000000 //@=0
1110001100001000 //M=D

M register in this case's location 0 in memory
A word about the m register, we can think of it as a virtual register