confusion regarding storage of program

dear all,

doubts:
1)i am using simens-300,400 plc for the system integration. i want to know that the program which we are downloading in plc will be stored in MMC or in Ram?
2) if it is in ram, then how can we transfer that program to our MMC?
3) suppose, we select such a cpu that the cpu having flash EPROM. then, where will be the program storage.
4) in s7-400 system, there is also eprom available and also battery available. so, what is the use of battery?

kinly refer to it and give me help for this.

Hi,
I know about MMC. It should be transfered automaticly. Try to see online what blocks are in memory of your PLC. If there is something(if not, then load any program to your PLC) try to delete the memory of your PLC(not from online). Then you can easily delete your PLC, turn to ON and see online what blocks are in memory. If they were on MMC you cannot easily delete them. You must do it from online viev selecting all the blocks and then deleting them.

I would describe it more precisely, but unfortunatelly I use german verision of Step7 and I don't know how to translate some words. If it is not clear for you I am sure somebody will explain it more clearly.