This book is intended to be a guide to SAS programming. SAS is a commercial statistical software. SAS help is known to be messy and it is often difficult to find relevant documentation on a specific issue in SAS programming. Note that the WPS software is another interpreter of the SAS language. There are lots of alternative to SAS. R is a free software and powerful statistical package. SPSS is easy to use. Stata is widely used in economics. SAS is especially adapted if you deal with very large datasets such as census data because it works directly on the data files without loading them in memory. Your contributions to this book are welcome.
There is also a Wikiversity course, Data Analysis using the SAS Language, which is organized by SAS functions and not by tasks.