HP-42S

This small but powerful calculator was designed to be software compatible with the HP-41C. It lacked the HP-41C's expandability but it offered, a two line dot matrix screen with customizable menus, greater speed, smaller size, and a lower price as compensation. The calculator had over 600 built-in functions. Obviously many of these were not printed on the keyboard but could be accessed by catalog, by typing their name after the XEQ key or by assigning them to the custom menu.