-#define SCK_OUT (DDRB |= BV(PB1)) // Load clock pin
-#define SOUT_OUT (DDRB |= BV(PB2)) // Serial in pin
-#define SLOAD_OUT (DDRB |= BV(PB3)) // Store clock pin
+#define SCK_OUT (DDRB |= BV(PB1)) // Shift register clock input pin
+#define SOUT_OUT (DDRB |= BV(PB2)) // Serial data input pin
+#define SLOAD_OUT (DDRB |= BV(PB3)) // Storage register clock input pin