nand2tetris/projects/04/mult/Mult.asm

// This file is part of www.nand2tetris.org
// and the book "The Elements of Computing Systems"
// by Nisan and Schocken, MIT Press.
// File name: projects/04/Mult.asm

// Multiplies R0 and R1 and stores the result in R2.
// (R0, R1, R2 refer to RAM[0], RAM[1], and RAM[2], respectively.)
//
// This program only needs to handle arguments that satisfy
// R0 >= 0, R1 >= 0, and R0*R1 < 32768.

// Put your code here.

// variable names are selfexplanatory
// itr temporary register at RAM[16]
@R2
M=0
@itr
M=0

// loop declaration
// D = R1 - itr
// if 0 jump to @STOP
// else continue
    (LOOP)
@itr
D=M
@R1
D=D-M
@END
D;JEQ

// R2 = R0 + R2
// itr = itr + 1
@R0
D=M
@R2
M=D+M
@itr
M=M+1

// back to loop declaration
@LOOP
0;JMP

// loopy loop
    (END)
@END
0;JMP