diff --git a/Assignments/4_Machine_Language/Fill.asm b/Assignments/4_Machine_Language/Fill.asm
new file mode 100644
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--- /dev/null
+++ b/Assignments/4_Machine_Language/Fill.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/04/Fill.asm
+
+// Runs an infinite loop that listens to the keyboard input. 
+// When a key is pressed (any key), the program blackens the screen,
+// i.e. writes "black" in every pixel. When no key is pressed, the
+// program clears the screen, i.e. writes "white" in every pixel.
+
+// Put your code here.
+(LOOP)
+@KBD
+D=M
+@BLACK
+D;JGT
+@R0
+M=0
+@CONTINUE
+0;JMP
+(BLACK)
+@R0
+M=0
+M=!M
+(CONTINUE)
+@31
+D=A
+@R1
+M=D
+@256
+D=A
+@R2
+M=D
+@SCREEN
+D=A
+@R3
+M=D
+(FILL)
+@R0
+D=M
+@R3
+A=M
+M=D
+D=A+1
+@R3
+M=D
+@R1
+DM=M-1
+@ENDOFLINE
+D;JEQ
+@FILL
+0;JMP
+(ENDOFLINE)
+@32
+D=A
+@R1
+M=D
+@R2
+DM=M-1
+@ENDOFSCREEN
+D;JEQ
+@FILL
+0;JMP
+(ENDOFSCREEN)
+@LOOP
+0;JMP
\ No newline at end of file
diff --git a/Assignments/4_Machine_Language/Mult.asm b/Assignments/4_Machine_Language/Mult.asm
new file mode 100644
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+++ b/Assignments/4_Machine_Language/Mult.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/4/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.)
+// The algorithm is based on repetitive addition.
+
+@R2
+M=0
+@R1
+D=M
+@END
+D;JEQ
+(STEP)
+@R2
+D=M
+@R0
+D=D+M
+@R2
+M=D
+@R1
+DM=M-1
+@STEP
+D;JGT
+@END
\ No newline at end of file