Before going into Rprogramming, let us know about SProgramming ! , "S" is a language used for analysing data , S is also a statistical language developed at Bell Labs and its still being evolved.
R is a language and environment for statistical computing and graphics.
Rlanguage is an implementation of Slanguage also R is open source (under GPL)
But where is R used ?
As R has wide functionalities in statistics and graphical techniques , they are used for :

linear and nonlinear modeling,

classical statistical tests,

timeseries analysis
R runs in machine with OS :

Windows

Unix like

Mac (no support for mac classic)
R has become the most popular language for data science and an essential tool for Finance and analyticsdriven companies such as :

Google,

Facebook, and

LinkedIn.
At the same time C is a general purpose language with different syntax that of R language
Reference :