We now have a structure that can be used to store any of four different kinds of data structures. The size of every record will be the size of that record containing the largest union. In this case part 1 is the largest union because it is composed of three integers, the others being composed of an integer and a character each. The first member of this union would therefore determine the size of all structures of this type. The resulting structure can be used to store any of the four types of data, but it is up to the programmer to keep track of what is stored in each variable of this type.
The variable "vehicle" was designed into this structure to keep track of the type of vehicle stored here. The four defines at the top of the page were designed to be used as indicators to be stored in the variable "vehicle". A few examples of how to use the resulting structure are given in the next few lines of the program. Some of the variables are defined and a few of them are printed out for illustrative purposes.
The union is not used too frequently, and almost never by beginning programmers. You will encounter it occasionally so it is worth your effort to at least know what it is. You do not need to know the details of it at this time, so don’t spend too much time studying it. When you do have a need for a variant structure, a union, you can learn it at that time. For your own benefit, however, do not slight the structure. You should use the structure often.
The variable "vehicle" was designed into this structure to keep track of the type of vehicle stored here. The four defines at the top of the page were designed to be used as indicators to be stored in the variable "vehicle". A few examples of how to use the resulting structure are given in the next few lines of the program. Some of the variables are defined and a few of them are printed out for illustrative purposes.
The union is not used too frequently, and almost never by beginning programmers. You will encounter it occasionally so it is worth your effort to at least know what it is. You do not need to know the details of it at this time, so don’t spend too much time studying it. When you do have a need for a variant structure, a union, you can learn it at that time. For your own benefit, however, do not slight the structure. You should use the structure often.
