Bravo, a document preparation program for the Alto produced at Xerox PARC by Butler Lampson, Charles Simonyi and colleagues in 1974, is generally considered to be the first program to incorporate the WYSIWYG technology, displaying text with formatting (e.g. with justification, fonts, and proportional spacing of characters). The Alto monitor (72 PPI, based on the typographic unit) was designed so that one full page of text could be seen and then printed on the first laser printers. When the text was laid out on the screen, 72 PPI font metric files were used, but when printed, 300 PPI files were used. As a result, one would occasionally find characters and words that are slightly off—a problem that would continue up to this day.