Data processing system for operating system with hierarchical user administration

The data processing system has an operating system with a login - procedure, at which an user of the data processing system can indicate a user name, which is put together from a first part and a second part. The first part of the user name is the same for all users of a user group, the second part of the user name is specific for each user of a user group. Some users of the system can be marked as privileged users, which have the authorisation to award valid user names within an user group, for which they may exercise this privilege. Members of an user group can be for their part again be other user groups, whereby the first part of the user name is put together from several parts according to the hierarchical structure of user groups, which clearly mark respectively an user group and their subgroups.