M icrosoft Windows  is a group of several  graphical   operating system  families , all of which are developed , marketed , and sold by  Microsoft . Active Windows families include  Windows NT  and  Windows Embedded   ; these may encompass su bfamilies, e.g.  Windows Embedded Compact  (Windows CE) or  Windows Server . Defunct Windows families include  Windows 9x ,  Windows Mobile  and  Windows Phone . The operating system for mainstream  personal computers ,  tablets  and  smartphones . The latest version is  Windows 10 . The main competitor of this family is  macOS  by  Apple Inc.  for personal computers and  Android  for mobile devices. Microsoft introduced an  operating environment  named  Windows  on November 20, 1985, as a graphical  operating system shell  for  MS-DOS  in response to the growing i...

A ' photocopier '  (also known as a  copier  or  copy machine ) is a  machine  that makes  paper copies of documents and other visual images quickly and cheaply. Most current  photocopiers  use a technology called  xerography , a dry process that uses electrostatic charges on a light-sensitive photoreceptor to first attract and then transfer toner particles (a powder) onto paper in the form of an image.  Heat, pressure or a combination of both is then used to fuse the toner onto the paper. (Copiers can also use other technologies such as  ink jet , but xerography is standard for office copying.) Earlier versions included the  Gestetner  stencil duplicator, invented by  David Gestetner  in 1881. Commercial xerographic office photocopying was introduced by  Xerox  in 1959, and it gradually replaced copies made by Verifax,  Photostat ,  carbon paper ,  mimeograph machines , and oth...