Question

I see lot of struct code like below

struct codDrives {
   WCHAR letter;
   WCHAR volume[100];
} Drives[26];

We can use variables or array something like that to store the data.

But I am not sure why would I use a struct in the programs?

Answer 1

Structs are inherited from C, and in C++ they are almost identical to classes. The difference is that the members of a struct are by default public, while class members are by default private.

So the typical use of structs in C++ is dummy data structures which contain no logic (only – possibly – constructors and/or necessary operators).

On a more general level, classes / structs are used to group together conceptionally related data pieces. E.g. for representing a person, you may need his/her first name, surname, gender, date of birth etc. It is convenient to define a struct containing all these pieces of data as members. Then you can store and pass around instances of this struct instead of a whole bunch of distinct variables. This makes the code cleaner, less error prone, more readable and easier to maintain.