Question about cooking pasta?

[shelleyh]

I am new to cooking. My question is, why when cooking pasta do we need to boil the water first then add the pasta? Why can't we put dry pasta and cold water into a pot then boil at once like when cooking oatmeal or rice? For instance, when boiling eggs, is there a difference if I boil water then add eggs and let it come to a boil again, or if I put eggs and water together then boil? I would really like to understand this. Thanks for your help