It is fair to say that the world would revolve at a far less speed if computer modelling and simulation programs disappeared overnight. Their use is found in the production of almost everything made, even the smallest of gadgets is first designed on a computer in an embedded graphics application. Everything from your toaster to your car, light bulb to your tea cup are first conceptualised in a computer program. The modelling however is different with each product and application.
Some modelling software will ascertain the flow of air over a car, another might calculate the drip and pour rate from a kettle or perhaps assess the fuel flow on a fighter jet s it screams the air at 800mph. There really is no limit to the use of computer modelling and as for simulation, that is a closer to home than you may have envisaged. Everybody from age seven upwards may have used a form of computer simulation in their own home.
Via computer games. So called simulation games like Civilisation or a game that involves taking control of a member of the armed forces to fight battles scenes use preprogrammed game mechanisms which calculate a response to every move.
While still complicated, this is computer simulation in its very basic element. As a user you change a part in the program and the computer replies with an answer. In computer simulation for technology and product development, you would be able to play in a similar way, the only difference is you would be inputting a response, a change in degree angle, shape, curvature or adding a new part.
Elsewhere in the world simulation is used for both entertainment and training, in fact many simulators in entertainment arcades and fairgrounds were at first simulation programs to train astronauts, pilots and drivers. Many programs are so sophisticated, that once you have undergone a thorough training program in a simulator, should a real world event occur that you have previously trained for in a simulator, you will be fully prepared to take the right actions in the real world.
Modelling and simulation software is used in every environment imaginable, even in place you wouldn't have considered. The streets and traffic lights are first modelled and them used as simulations to prepare for roll out and proper road traffic control. Supermarket malls use population footfall to assess emergency exists and overcrowding and correct placement of shop entrances.
We may be humans, but without computer modelling and computer simulation software, we would not have attained the level of standard in living across the board with such rigid communal systems without the aid of a computer and its various utilities to assess dangers and make products more advanced.