The WINDOWSTYLE attribute defines the style to be used by the parent window of a form.
WINDOWSTYLE = "string"
The WINDOWSTYLE attribute can be used to specify the style of the parent window that will hold the form. This attribute is specific to the LAYOUT element. Do not confuse this attribute with the STYLE attribute, which is used to specify the decoration style of the form elements.
When a form is loaded by the OPEN WINDOW or DISPLAY FORM instruction, the runtime system automatically assigns the WINDOWSTYLE to the STYLE attribute of the parent window element.
LAYOUT ( STYLE="BigFont", WINDOWSTYLE="dialog" )