diff --git a/module00/ex01/main.c b/module00/ex01/main.c
index 676b247..fe04856 100644
--- a/module00/ex01/main.c
+++ b/module00/ex01/main.c
@@ -5,6 +5,11 @@
 #define TEST(REGISTER, BIT)		REGISTER & 1 << BIT
 #define TOGGLE(REGISTER, BIT)	REGISTER ^= 1 << BIT
 
+#define D1 0
+#define D2 1
+#define D3 2
+#define D4 4
+
 int main()
 {
     // DDRx : select direction of the pin
@@ -20,18 +25,17 @@ int main()
     // PINx : 
 
 
-    // turn on led 1
-    SET(DDRB, 0);		// make PB0 as OUTPUT
-    SET(PORTB, 0);		// make PB0 as HIGH (LED turns ON)
+    SET(DDRB, D1);		// make PB0 as OUTPUT (pullup is off)
+    CLEAR(PORTB, D1);	// make PB0 as HIGH (LED turns ON)
 
-    // CLEAR(DDRB, 1);		// make PB0 as INPUT
-    // SET(PORTB, 1);		// make PB0 pullup on
+    // SET(DDRB, D2);		// make PB1 as OUTPUT (pullup is off)
+    // CLEAR(PORTB, D2);	// make PB1 as LOW (LED turns OFF)
 
-    // SET(DDRB, 2);		// make PB0 as OUTPUT
-    // CLEAR(PORTB, 2);		// make PB0 as LOW (LED turns OFF)
+    // CLEAR(DDRB, D3);		// make PB2 as INPUT
+    // SET(PORTB, D3);		// make PB2 pullup on
 
-    // CLEAR(DDRB, 4);		// make PB0 as INPUT
-    // CLEAR(PORTB, 4);		// make PB0 as LOW (LED turns OFF)
+    // CLEAR(DDRB, D4);		// make PB4 as INPUT
+    // CLEAR(PORTB, D4);	// make PB4 pullup off
 
     return 0;
 }
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