h6. [[OS SWI Calls]] h6(. » OS_CheckModeValid h2. OS_CheckModeValid h5. (SWI &3F) |_<^{width:3em}. Entry | | |<^. R0 |<^. Screen mode to check (either [[Screen Modes|mode number]] or [[Mode Specifier Block]]) | |_<^{width:3em}. Exit | | |\2<^. If C flag unset, then Screen mode is valid| |<^. R0|<^. Preserved| |\2<^. If C flag set, then Screen mode is invalid| |/2<^. R0|<^. -1 = Screen mode is non-existent| |<^. -2 = Not enough memory| |/2<^. R1|<^. Alternative screen mode to use| |<^. -2 = Unable to select alternative screen mode| h4. Use The purpose of this call is to check if it is possible to change to a specified screen mode. h4. Notes This finds out whether you may change to a given mode or whether it is invalid, for example if the mode isn't supported by the current monitor type or if there is no suitable MDF entry for a [[Mode Specifier Block]]. If the mode is invalid then the returned value in R0 will indicate the reason why, and R1 may contain a suggested alternative mode. h4. See also * [[Screen Modes]] * [[Mode Specifier Block]]