Abstract: A method and apparatus for visually comparing two files or portions thereof by visually indicating to the user areas of identity and differences between the items being compared. The items are stored in a video RAM which controls the visual presentation on the screen. The respective pixel settings in the video RAM are exclusively or'ed and the results are then stored in the video RAM so that the difference between the two items are displayed. A user can edit each item, while the comparison is being made, so that the effect of the editing on the differences, is immediately shown and apparent to the user.

Abstract: Smooth scrolling of a document on an all points addressable system which provides fast response and scrolling in increments of a single display row, while being storage efficient. The document is completely stored in compact format and a portion of the document which encompasses the current display window is stored in bitmap image format. There is smooth scrolling between displays completely within the bitmap image. The scroll is only interrupted for a scroll outside the portion of the document in bitmap image format, in which case the bitmap image is adjusted using the compact format to include that portion of the document with the desired display.