ISO/IEC 9995-4:2009

ISO/IEC 9995 defines a framework for the layout of all alphanumeric and numeric keyboards across the widest spectrum of today's and upcoming applications using keyboards. The functions to be performed by keyboards are grouped into three categories that correspond to the main physical sections of the keyboard.
Application of ISO/IEC 9995 in the design of keyboards will provide the user with a unified, predictable user-machine interface by dividing the keyboard into functional areas and sections and allocating functions to keys.
ISO/IEC 9995-4:2009 specifies the numeric section of a keyboard and the division of that section into zones. It specifies the arrangement, the number, and the location of the keys in the numeric zone ZN0 and in the function zones ZN1 to ZN6 of the numeric section, as well as the allocation of functions to the keys.
The numeric zone ZN0 is to be used in keyboards for applications such as text and data processing, general office environment, banking, point of sales (POS), telematic services, telephony apparatus, home electronic systems, numerical control of machinery and equipment, and input of personal identification number (PIN). The function zone ZN1 is to be used in keyboards for applications such as data entry, text and data processing, and general office environment.