I'm having trouble thinking up a script to add a text i designate, to the beginning and end of each line, in a text file.

For example, let's say I had a text file with 100 lines of things like..
How Ya Doin
What ya up to
..etc, how could I make it add, let's say.."whatever" to the beginning of each line, and "idontthinkso" to the end of each line?

Anyone got any idas?