How to add .h file in library I am trying to make an ultrasonic distance meter using Arduino. For this I added the ultrasonic library. But on compiling it shows this error "ultrasonic.h
not available". Please tell me how to add this .h file.
In you Arduino Sketch folder there is a folder called Libraries, create a folder there and put your header file in that folder and restart the Arduino IDE.

For example (PC):

Documents/Arduino/Libraries/ultrasonic/ultrasonic.h


You can now use it in all your projects.

If you only want to use with a particular sketch, place in in the same folder as you  sketch and restart Arduino IDE.