New to R and RStudio, the problem is with RStudio.
I have an example code about 53 lines, I could exit by typing "q ()" or "quit ()", but after running any code (highlighted section or all codes), "q ()" will not work, as shown in figure below 
Or, if I try to close the RStudio browser, the notification shown below appears, but it never closes. 
Any hint?
Thank you very much!
PS: RStudio verson: 0.99.948
----- 1st Update ------ @ Mike the Wise
I tried to get session information by typing "sessionInfo ()" in the console, unfortunately there is no answer ... pic below 
Again, this case only happens after running my code
----- 2nd Update ------ - execute sessionInfo () before running the code:
Information as below:
R version 3.2.3 (2015-12-10) Platform: x86_64-w64-mingw32 / x64 (64-bit) Running under: Windows 7 x64 (build 7601) Service Pack 1
locale: 1 LC_COLLATE = English_United States.1252 LC_CTYPE = English_United States.1252 LC_MONETARY = English_United States.1252 [4] LC_NUMERIC = C
LC_TIME = English_United States. 125
attached basic packages: 1 grDevices utilization statistics
dataset method base
loaded via a namespace (and not attached): 1 tools_3.2.3
My code is:
# Linear Regression in R
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