Abstract: The invention relates to a combination of a computer keyboard and an extension unit for providing user input to a computing device, e.g. a computer, wherein the keyboard comprises: a housing; buttons and/or keys held by the housing; an electronic module accommodated inside the housing to convert engagement with a button or key into coded form and to transmit the coded form to the computing device as user input, wherein the extension unit comprises: a housing; a button and/or key held by the housing; an electronic module accommodated inside the housing to convert engagement with a button or key into coded form and to transmit the coded form to the electronic module of the keyboard for further transmittal to the computing device as user input, and wherein the keyboard and the extension unit are configured to releasably attach the housing of the extension unit to the housing of the keyboard at a plurality of different locations.