diff --git a/Operators/MASK.agc b/Operators/MASK.agc
new file mode 100644
index 0000000..1969827
--- /dev/null
+++ b/Operators/MASK.agc
@@ -0,0 +1,15 @@
+# Minimal demo of the MASK operator.
+
+		SETLOC	4000
+		INHINT
+
+				# MASK bitwise ANDs the 'A' register with another number.
+
+		CAF NINE		# Load 9 into 'A' register.
+		MASK TWELVE		# AND 9, 12.
+		NOOP		# 'A' register now contains 8 (1000).
+
+END		TCF END
+
+NINE		DEC	9	# 1001
+TWELVE		DEC	12	# 1100
diff --git a/Operators/MP.agc b/Operators/MP.agc
index 5c418cd..9f4ba2d 100644
--- a/Operators/MP.agc
+++ b/Operators/MP.agc
@@ -5,7 +5,7 @@
 
 				# MP multiplies the 'A' register with another number.
 
-		CAF SIX		# Load 5 into 'A' register.
+		CAF SIX		# Load 6 into 'A' register.
 		EXTEND
 		MP SEVEN		# Multiply 6 * 7.
 		NOOP		# 'L' register now contains 42.