Affects several elements differently - that is, its behavior is element dependent. It is often used to change the control's main value, such as the text of a IupText.
For the IupRadio and IupZbox, elements, which are categorized as composition elements, this attribute represents the element "selected" among the others in the designed composition. To change this attribute in such cases, different mechanisms are necessary according to the programming environment used. When the elements taking part in a composition were created in C, this attribute's contents is a name that must be defined by the IupSetHandle function. When the elements were created in Lua, this attribute's contents is the name of a variable - more precisely, the one receiving the return from the function that created the element you wish to select. In LED it is not possible to dynamically change the value of any attribute, so the elements created in this environment must be identified and manipulated in C by means of their identifying name.