PLC Memory

Hello guys
for siemens S7-300

is the main programe stroed on plc ROM(Micro Memory Card)?

what kind of data stored on RAM?

if the backup battary finished will I shutdown PLC first or not at replacing?

How can I take backup copy on my computer?

You can find all siemens manuals at siemens website.

For S7-300 it goes like:

If the PLC has a MMC, then it won't have batteries.
If the PLC has batteries, then you never ever shut it down when you replace the batteries.

Taking back-up is done with Simatic Manager software.