The root picture

For devices that allow the memories to be scrolled independently there is a potential conflict when searching for a picture. This occurs because under normal conditions a picture can only be recalled from the database if it lies within the current picture. If the pictures are located on different memory planes then this can be negated by scrolling one of the memories. To overcome this a more general search is allowed by selecting the root picture which contains all other pictures (including the base picture). A call to the routine AGI_SROOT selects the root picture. A subsequent call to any of the recall routines AGI_RC* will obtain the relevant picture without it having to lie within the current picture. The root picture is deselected in the recall routine, and so AGI_SROOT has to be called on every occasion that an unlimited search is to be made. Recall is the only operation allowed with the root picture. Any other operation called while the root picture is selected will result in the previously current picture being used.