The R4DS is often seen as a great purchase. This is because there are so many great things that can be done with one. For example, you can install Moonshell on it to organise your files on the SD card. More importantly Moonshell is an operating system for R4DS and it also has nifty features like calculator, basic word processing and file management. It is similar to Window or Linux in this respect. A version of Linux is also available to the R4DS to use as an operating system. The Linux R4DS operating system is available for free download.