diff --git a/blackboard.xsa b/blackboard.xsa
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diff --git a/src/main.s b/src/main.s
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+.text
+.global main
+
+@define constants, these can be used as symbols in your code
+.equ LED_CTL, 0x41210000
+.set SW_DATA, 0x41220000
+
+@the set and equ directives are equivalent and can be used interchangeably
+
+main:
+	ldr r1,=SW_DATA	@load switch address from constant
+	ldr r2,=LED_CTL	@load LED address from constant
+loop:
+	ldr r0,[r1]	@load switch value *r1 ->r0
+	str r0,[r2]	@store value to led register *r2 <-r0
+	b loop		@go back to "loop"
+
+.end