Page "HP-41C" Paragraph 3

The calculator had a special user mode where the user could assign any function to any key if the default assignments provided by HP were not suited to a specific application.

For this mode, the HP-41C came with blank keyboard templates ; i. e. plastic covers with holes for the keys, so the user could annotate customized keys.

Hewlett-Packard even sold a version of the calculator where hardly any keys had function names printed on them, meant for users who would be using the HP-41C for custom calculations only ( thus not needing the standard key layout at all ); this version of the calculator was colloquially known, within HP's Corvallis calculator team, as a " Blanknut " ( because the development code name for the HP-41c's processor was known as the " coconut ").