Final answer:
Tagged structures have a name associated with them and can be used to declare variables, while untagged structures can only define variables within a program. Nested structures allow you to group data in a hierarchical manner. Arrays of structures allow you to store multiple instances of the same structure.
Step-by-step explanation:
Tagged and Untagged Structures:
In C++, structures are used to group related data together. A tagged structure is a structure that has a name, or a tag, associated with it. This tag allows you to declare variables of that structure type. An untagged structure, on the other hand, does not have a name associated with it and can only be used to define variables within a program
A nested structure is a structure that is defined within another structure. It allows you to group data in a hierarchical manner. Here's an example:
#include <iostream>
struct Person {
 std::string name;
 int age;
};
struct Address {
 std::string street;
 std::string city;
 std::string state;
};
struct Employee {
 Person personalInfo;
 Address addressInfo;
};
int main() {
 Employee employee;
 employee.personalInfo.name = "John Doe";
 employee.personalInfo.age = 25;
 employee.addressInfo.street = "123 Main St";
 employee.addressInfo.city = "New York";
 employee.addressInfo.state = "NY"; 
 return 0;
}
Combination of Structures and Arrays:
In C++, you can use arrays of structures to store multiple instances of the same structure. Here's an example:
#include <iostream>
struct Student {
 std::string name;
 int age;
};
int main() {
 const int SIZE = 3;
 Student students[SIZE];
 
 students[0].name = "Alice";
 students[0].age = 18;
 
 students[1].name = "Bob";
 students[1].age = 19;
 
 students[2].name = "Charlie";
 students[2].age = 20;
 
 return 0;
}