This special pen was invented by Liu Jie. He invented it because he always need to take notes quickly. It has three colors and is used for taking notes quickly. It is very useful if you have a lot to write down. The pen comes with a microchip that can store a list of common words that you will use. You can program the words you will use often into the microchip’s memory, then assign a short form to each word. When you are writing, you just need to write the short forms with the pen, press a button on the pen and all the short forms will change into the actual words. The microchip can contain up to 50 words and you can make changes to the list of words whenever you need to.

What problem does Liu Jie have?

What is it used for?