difference between at89c51 & at89s51

Could any body tell me abot the difference betwin 89c51 & 89s51

in the data sheet i got the pins status are the same but the flash memory of both mcu is in system programmable but the 89s51 only have pins allocated for in system programming. what about 89c51 pins for in systemm programming?

89C or 89S

89C51 is discontinued not recommended for new design(according to atmel)

The main difference is the ISP programming. 89C51 needs parallel programmming only, NO SPI.

89S51 is real easy to program in system.