atoi Function

In order to make use of a number when entered, we must first convert it from a string of characters into an actual integer. The function for performing this conversion is the atoi function from the stdlib library. It takes a string as its single parameter and it returns an int. The only difficulty with this is that, as things are, the string of characters representing our number is not currently terminated with a \0. It just exists as a subset of the characters in our full string.