MacPaint uses two offscreen memory buffers to avoid flicker when dragging shapes or images across the screen.[8] One of these buffers contained the existing pixels of a document, and the other contained the pixels of its previous state.[8] The second buffer was used as the basis of the software's undo feature.[8] In April 1983, the software's name was changed from MacSketch to MacPaint.[9] The original MacPaint was programmed as a single-document interface. The palette positions and sizes were unalterable, as was the document window. This differed from other Macintosh software at the time, which allowed users to move windows and resize them.