An anonymous reader notes that Microsoft has been granted a patent on "Page Up" and "Page Down" keystrokes
. The article links an image of an IBM PC keyboard from 1981
with such keys in evidence. "The software giant applied for the patent in 2005, and was granted it on August 19, 2008. US patent number 7,415,666 describes 'a method and system in a document viewer for scrolling a substantially exact increment in a document, such as one page, regardless of whether the zoom is such that some, all or one page is currently being viewed.'... The company received its 5,000th patent from the US Patent and Trademark Office in March 2006, and is currently approaching the 10,000 mark."