The document provides an overview of structures in C++ programming, illustrating how to define, initialize, and manipulate structures to store complex data types such as student information. It discusses accessing structure members, using structures as function arguments, and the benefits of nesting structures for better data organization. Additionally, it includes examples of dynamically allocating structures and managing memory with pointers.

1. Structures
Chapter 4

2. Introduction
• Suppose you want to store information about students
in a class
– Assuming that the class has 5 students
• You might want to store their names, addresses, and
grades
2

3. Introduction
string name[5] = {“Tom”, “Jerry”, “Pluto”,
“Donald”, “Mickey”};
string adr[5] = {“12 Cat st.”,
“34 Mouse st.”,
“56 Dog st.”,
“78 Duck st.”,
“90 Mouse st.”};
float grade[5] = {1.1, 3.3, 5.5, 7.7, 9.9};
for (i = 0; i < 5; i++)
cout << name[i] << adr[i] << grade[i];
3

4. Introduction
for (i = 0; i < 4; i++)
for (j = i + 1; j < 5; j++)
if (name[i] > name[j])
swap(name[i] > name[j]);
for (i = 0; i < 5; i++)
cout << name[i] << adr[i] << grade[i];
// {“Donald”,“Jerry”,“Mickey”, “Pluto”, “Tom”}
// {1.1, 3.3, 5.5, 7.7, 9.9}
4

5. C++ Structures
• A structure is a user-defined type
• A single structure can hold items of more than one data
type
• How to define a structure type?
struct <tag> {
<type 0> <member/field name 0>;
<type 1> <member/field name 1>;
…
}; 5

6. C++ Structures
struct student {
string name;
string adr;
float grade;
};
student a, b, * ps, group[5];
6

7. Accessing Structure Members
• The dot operator is used to access structure members
<name of structure variable>.<member name>
cout << "Enter the student's name: ";
getline(cin, a.name);
cout << "Enter the student's address: ";
getline(cin, a.adr);
cout << "Enter the student's grade: ";
cin >> a.grade;
cout << a.name << a.adr << a.grade;
group[0] = a;
cout << group[0].name << group[0].adr <<
group[0].grade; 7

8. Structures as Function Arguments/Return Values
• Consider the following function prototypes:
void sortData(student []);
void inputItem(student &);
student inputItem();
student * inputItem();
void outputItem(student);
void outputItem(student *);
8

9. Initializing a Structure
• The members of a structure variable may be initialized
with starting values
student a = {"Tom", "12 Cat st.", 1.1};
student group[5] = {
{"Tom", "12 Cat st.", 1.1},
{"Jerry", "34 Mouse st.", 3.3},
{"Pluto", "56 Dog st.", 5.5},
{"Donald", "78 Duct st.", 7.7},
{"Mickey", "90 Mouse st.", 9.9}
};
9

10. Pointers to Structures
• Similar to define pointers to built-in types, you may
define pointers to structures
student a, * p, * q, group[5];
p = &a;
q = group;
• In general, there are three ways to access structure
members
a.name p->name (*p).name
10

11. Dynamically Allocating a Structure
• You can use a structure pointer and the new operator to
dynamically allocate a structure
student * p;
p = new student;
getline(cin, p->name); getline(cin, p->adr);
cin >> p->grade; …; delete p;
• You can also dynamically allocate an array of structures
student * group;
group = new student [10];
getline(cin, group[5].name);
cin >> group[5].grade; …
delete [] group; 11

12. Pointers As Members
• Sometimes structures contain pointers as members
struct ABC {
int * ptr;
};
ABC a, * p;
• Consider several ways to access a pointer that is a
member of a structure
a.ptr ⇔ p->ptr ⇔ (*p).ptr
*a.ptr ⇔ *p->ptr ⇔ *(*p).ptr
12

13. Pointers As Members
struct ABC {
int * ptr;
};
ABC a, b;
a.ptr = new int [N];
b.ptr = new int [N];
a = b;
delete [] a.ptr;
delete [] b.ptr; // ???
13

14. Nested Structures
• Consider the following type definition
struct student {
string name;
string adr;
float grade;
int dayOfBirth;
int monthOfBirth;
int yearOfBirth;
};
• It would be better if all information related to date of
birth is unified into a single structure …
14

15. Nested Structures
struct dateOfBirth {
int day, month, year;
};
• … and the new structure is nested inside struct
student
struct student {
string name;
string adr;
float grade;
dateOfBirth birthDate;
};
15

16. Nested Structures
struct dateOfBirth {
int day, month, year;
};
• … and the new structure is nested inside struct
student
struct student {
…
dateOfBirth birthDate;
};
student a;
cin >> a.birthDate.day;
student b = {"Tom", "Cat st.", 1.1, {1,2,3}};
16

17. Case Study
Write a program that uses a structure to store the following data:
17
Member Name Description
Name Student name
Tests Pointer to an array of 𝑘 test scores
Average Average test score
• The program should keep a group of students
• It should ask the user how many test scores there are to be and
how many students there are
• It should then dynamically allocate an array of structures
• Each structure’s Tests member should point to a dynamically
allocated array that will hold the test scores
A list of students that are sorted by Average in descending order
should be displayed on the screen