How exactly does a country devalue its currency?
Does some official tell the Foreign Exchange the the new exchange rate for the yuan is 0.98 * the current exchange rate? For China (and other countries with fixed/controlled exchange rates) - that's exactly how it happens. Does it just print more? This is the way to go for fully convertible currencies (like the USD, EUR, GBP, and handful of others, there're about 20 in the world). Flood the market and as with any commodity - flooding the market leads to a price drop. Obviously "just print more" is much harder to do than picking up the phone and saying "Now you're buying/selling dollars at this price and if you don't I'll have you executed".