Update checks the OS platform before changing directories. Also added message when switching to lookup mode.

main.py

@@ -38,10 +38,13 @@ while True:
     elif command == 'CARD':
         Card = 1
     elif command == 'UPDATE':
-        os.system('cd ~/libraryClient')
-        os.system('git pull')
+        if os.name != 'nt':
+            os.system('cd ~/libraryClient')
+        else:
+            os.system('git pull')
     elif command == 'LU':
         Mode=3
+        print('Mode lookup')
     elif command == '':
         pass
     else: