What's an UNIX OS technically in 1Sentence.

A Unix-like operating system is
a "Software" collection of
applications,
libraries, and developer tools,
plus a program to allocate resources
and talk to the hardware, known as a kernel.

http://www.gnu.org/

Field of View FoV, use your fist it's 10degrees wide, Full Frame!

To get an idea of how much is a "numerical" FoV say 30degrees?
Clinch your hand into a fist, and keep it stretched away from the eyes, n what your fist covers Horizontally is about 10degrees.

Non-Full Framer should use the (Multiplier 1.6) effective Focal Length.