"its the same as C"

The language is the same, but you need to be careful how you use the language if you want an efficient & effective embedded system.

Any embedded 'C' compiler will have language extensions and/or restrictions due to the nature of its target; you will need to read the compiler Manual carefully to determine how to write "good" embedded 'C' for your particular target.

Keil's C51 manual has a chapter dedicated to writing efficient 'C' for the 8051 (the PDF manual is inculded in the FREE evaluation download).

Another article to look for is "THE FINAL WORD ON THE 8051" by Matthew Chapman.
This used to be on the free Keil CD, but I think they've recently dropped it. :-(
However, it's quite widely published, so a search here or at your favourite internet search engine should soon locate a copy.

The Ganssle Group has a wealth of articles on Embedded Systems at:
http://www.ganssle.com/articles.htm