An O.S. can be an operating system as well as this type of software like Firefox, GIMP & Thunderbird
The 
operating system and most of its software are created by volunteers and ... 
Popular applications like Firefox, Thunderbird, OpenOffice, VLC, Gaim/Pidgin, 
The GIMP,... [DOC] [TLE] Simplicity Linux - A small, fast and versatile Linux distro [PAR] Aug 29, 2016 ...