feat: added unit 04 material

project-4-machine-language/provided-asm-files/Add.asm

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+// This file is part of www.nand2tetris.org
+// and the book "The Elements of Computing Systems"
+// by Nisan and Schocken, MIT Press.
+
+// Computes R0 = 2 + 3  (R0 refers to RAM[0])
+
+@2
+D=A
+@3
+D=D+A
+@0
+M=D

project-4-machine-language/provided-asm-files/Max.asm

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+// 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/6/max/Max.asm
+
+// Computes R2 = max(R0, R1)  (R0,R1,R2 refer to RAM[0],RAM[1],RAM[2])
+// Usage: Before executing, put two values in R0 and R1.
+
+// R0 = 10
+// R1 = 15
+// d = 10
+// d = 10 - 15
+
+  // D = R0 - R1
+  @R0
+  D=M
+  @R1
+  D=D-M
+  // If (D > 0) goto ITSR0
+  @ITSR0
+  D;JGT
+  // Its R1
+  @R1
+  D=M
+  @OUTPUT_D
+  0;JMP
+(ITSR0)
+  @R0
+  D=M
+(OUTPUT_D)
+  @R2
+  M=D
+(END)
+  @END
+  0;JMP

project-4-machine-language/provided-asm-files/Rect.asm

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+// 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/6/rect/Rect.asm
+
+// Draws a rectangle at the top-left corner of the screen.
+// The rectangle is 16 pixels wide and R0 pixels high.
+// Usage: Before executing, put a value in R0.
+
+   // If (R0 <= 0) goto END else n = R0
+   @R0
+   D=M
+   @END
+   D;JLE
+   @n
+   M=D
+   // addr = base address of first screen row
+   @SCREEN
+   D=A
+   @addr
+   M=D
+(LOOP)
+   // RAM[addr] = -1
+   @addr
+   A=M
+   M=-1
+   // addr = base address of next screen row
+   @addr
+   D=M
+   @32
+   D=D+A
+   @addr
+   M=D
+   // decrements n and loops
+   @n
+   MD=M-1
+   @LOOP
+   D;JGT
+(END)
+   @END
+   0;JMP