The ideal gas law is an empirical law; it's a relationship between the pressure in a system of gases to the volume, the temperature, and the number of gas atoms/molecules in the system. This "law" is valid if the gas atoms/molecules are infinitely small and do not interact (ideal), but real gases are not ideal (even noble gases have attraction and volume). Nonetheless the ideal gas laws and equations do an excellent job of describing the behaviors of gases (particularly the noble gases). The ideal gas law was developed by combining sets of famous more simple gas laws that were each established through clever experiments. Each of these gas laws is named after the scientist who discovered it, and these laws were all discovered long before the invention of computers.