how is data affected if the same constant is added..?

I had to obtain results for specific data, and now I have a question that I don't understand.

How is the mean, median and standard deviation affected if the same constant is added to every value in the data set?

I'm not sure, but I thought that the whole distribution shifts by that constant. And the mean becomes original mean+ a (the constant). But I am still stumped as to how the standard deviation is affected.

Any help with this question is greatly appreciated..thanks!