You will find detailed information in the original CART book by Breiman et al.: Breiman, L., Friedman, J., Stone, C. J., & Olshen, R. A. (1984). Classification and regression trees. CRC press.

You will find chapters on CART in nearly every book on statistical learning/ machine learning/ data mining topics. I recommend the respective chapter in Hastie et al. (2009). The elements of statistical learning. 2001. New York: Springer.

The reference manuals for R packages always provide example code, see http://cran.r-project.org/web/packages/rpart/rpart.pdf for the CART implementation in R (package "rpart"). A detailed introduction to the rpart- package can be found here: http://cran.r-project.org/web/packages/rpart/vignettes/longintro.pdf