Post your example of a real world function here--from Exercise 1.8.
An example of an everyday "real life" function would be that depending on the weather makes a person decide what type of clothing and the amount of clothing they will wear. For example, if it is hot outside you wear less clothing; like a t-shirt and shorts. However, if it is cold, you will wear more clothing like jeans, long sleeve shirt, leggings, and a coat or even more.
One example from a sports related view is basketball. The input of basketball player with the amount of time spent practicing shooting free throws. The output becomes a higher percentage of shots made. The player practices more therefore he performs better because he put in more time.