I just plugged my arduino and click upload, it shows this error:
Arduino: 1.8.5 (Windows 7), Board: "Arduino/Genuino Uno" Sketch uses 948 bytes (2%) of program storage space. Maximum is 32256 bytes. Global variables use 9 bytes (0%) of dynamic memory, leaving 2039 bytes for local variables. Maximum is 2048 bytes. avrdude: ser_open(): can't open device "\\.\COM1": The system cannot find the file specified. Problem uploading to board. See http://www.arduino.cc/en/Guide/Troubleshooting#upload for suggestions. This report would have more information with "Show verbose output during compilation" option enabled in File -> Preferences.