I need to know how to download all addresses of some area from openstreet maps? After that I want to place all addresses in csv file.
while looking for OSM download functions, I once came across the "overpass-turbo" tool (see http://overpass-turbo.eu/). Although it requires quite some time to get into it and all necessary query commands, it might do what you need.
Please refer also to the according wiki: http://wiki.openstreetmap.org/wiki/Overpass_API/Overpass_QL
You can find examples for a "CSV output mode" for a specified area.
A similar helpful discussion can be found here: How do I get the building housenumber from OSM data?