project04: Complete mult.asm

04/mult/Mult.asm

@@ -7,4 +7,36 @@
 // (R0, R1, R2 refer to RAM[0], RAM[1], and RAM[2], respectively.)
 // The algorithm is based on repetitive addition.
 
-//// Replace this comment with your code.
+// excuse excessive comments here..
+
+    // init r2 to 0
+    @2 // sel r2
+    M=0 // set it to 0
+
+(LOOP) // begin loop
+
+    // check if r1 = 0
+    @1 // sel r1
+    D=M // load r1 to data from mem
+    @END // sel END
+    D;JEQ // jump to END if r1 = 0 (nothing left to add, we're done)
+
+    // add r0 to r2
+    @2 // sel r2
+    D=M // load r2 to data
+    @0 // sel r0
+    D=D+M // add r0 to r2 (r2 in mem, r0 in data)
+    @2 // sel r2
+    M=D // store result in r2
+
+    // r1 -= 1 (decrement)
+    @1 // sel r1
+    M=M-1 // decrement r1
+
+    // check if r1 = 0 (jump back)
+    @LOOP // sel LOOP
+    0;JMP // jump to LOOP
+
+// end
+(END) // label for jump
+    0;JMP // from textbook, infinite loop?