By "mc" I presume you mean "microcontroller"?
It's always best to write these things out in full, at least the first time - don't just assume that people will automatically recognise your abbreviations!


and SMS abbreviations like 'u'" should be avoided altogether.


For an 8051, you need to load your executable image into the CODE space - whether that is physically implemented as ROM or RAM depends upon your particular target hardware.
(in most cases, it will usually be ROM or PROM of some sort).


What is "flash ram"?

"Flash" is a type of electrically eraseable PROM;
"RAM" is usually taken to mean read/write memory - such as SRAM (in 8051 contexts) or DRAM (more generally).

So, "flash ram" would be a contradiction in terms - perhaps you mean "Flash ROM" (or "Flash PROM")...?

How you use the specific features of a particular chip depends upon the chip in question! See the Datasheet, and other supporting materials on the manufacturer's website for details.


What do you want to use it for?
Who said you need to use it?


So use it, then!

For a basic introduction to the 8051 see the FAQs and Tutorials on this site, and the so-called "bible" for the 8051:

Chapter 1 - 80C51 Family Architecture:
http://www.nxp.com/acrobat_d...ARCH_1.pdf

Chapter 2 - 80C51 Family Programmer’s Guide and Instruction Set:
http://www.nxp.com/acrobat_d...UIDE_1.pdf

Chapter 3 - 80C51 Family Hardware Description:
http://www.nxp.com/acrobat_d...WARE_1.pdf


And check-out these book lists:
http://www.keil.com/books/8051books.asp
http://www.8052.com/books.phtml