The P4 contained the same chips as the PHILIPS: P210 but the display and the keys were different and had to be connected to the mains. It was demonstrated at the 1972 International Solid-State Conference. Showing the P4 there, was not a pleasant experience, knowing that there was already a real Pocket Calculator (P210) in the PHILIPS Research Labs. On top of it, at the same conference, the HP: 35 (the first pocket calculator to contain all the functions of a Slide Rule) made it clear the HEWLETT-PACKARD was far ahead in this technology.