If you look on the left <-- , you will see the tutorial icon.In there you will find the info your after.
The AT89S8252 is another variant of the 8051 architecture , and so by learning the basic 8051 commands you open the door to an ever expanding line of products.
The two best supported/performing and upto date C compilers are the Keil c51 and the Raisonance (again see links on left) You can download demo's,but the Keil is effectively crippleware , where as the Raisonance is limited to 4k,but has full in all other respects.

The Raisonance does not use dongles , where as Keil do(but not in America --Why is that John Ward.My computer sticks out 3 feet cos of bloody dongles)