This is a SHARP pocket computer, the PC-G850VS. My son purchased it when he entered high school and used it for only a few months, up until the summer break of his first year. There is no instruction manual. I have confirmed that the power turns ON and OFF with batteries inserted, and that basic button operations work. However, please understand that I have not checked all functions due to my lack of knowledge. Please understand that I cannot guarantee the functionality of all operations, and consider purchasing accordingly. Please understand that there may be scratches, damage, or dirt on the main unit that are not shown in the photos or described in the product description due to oversight. This is an old item that has been stored by an individual for a long time, so please refrain from purchasing if you are sensitive to such things. Returns and exchanges are not possible, so please be aware of this. The outer box and AAA batteries are not included.