diff --git a/Code/C_Code/23.1.1_SenseLED/SenseLED.c b/Code/C_Code/23.1.1_SenseLED/SenseLED.c
index 395e0c1..898fee1 100644
--- a/Code/C_Code/23.1.1_SenseLED/SenseLED.c
+++ b/Code/C_Code/23.1.1_SenseLED/SenseLED.c
@@ -22,11 +22,11 @@ int main(void)
 
 	while(1){
 		
-		if(digitalRead(sensorPin) == HIGH){ //sensor has pressed down
+		if(digitalRead(sensorPin) == HIGH){ //if read sensor for high level
 			digitalWrite(ledPin, HIGH);   //led on
 			printf("led on...\n");
 		}
-		else {				//sensor has released 
+		else {				
 			digitalWrite(ledPin, LOW);   //led off
 			printf("...led off\n");
 		}
diff --git a/Code/Python_Code/22.1.1_MatrixKeypad/MatrixKeypad.py b/Code/Python_Code/22.1.1_MatrixKeypad/MatrixKeypad.py
index 66dc61d..1141fab 100644
--- a/Code/Python_Code/22.1.1_MatrixKeypad/MatrixKeypad.py
+++ b/Code/Python_Code/22.1.1_MatrixKeypad/MatrixKeypad.py
@@ -4,6 +4,7 @@
 # Author      : freenove
 # modification: 2016/07/13
 ########################################################################
+import RPi.GPIO as GPIO
 import Keypad       #import module Keypad
 ROWS = 4        # number of rows of the Keypad
 COLS = 4        #number of columns of the Keypad
diff --git a/Tutorial.pdf b/Tutorial.pdf
index 31f0f4f..fbad36a 100644
Binary files a/Tutorial.pdf and b/Tutorial.pdf differ