1. Programmer Defined Structures (Records)
CS362

2. C++ Structures
A Structure (Record) Contains Data About a Single Entity:
Each Data Item is Called a Member (or Field)
Members Can Be Of Different Data Types
Member Data Types Can Be Basic or Complex
Basic – int, float, double, string
Complex – array, other structures
In The End, Any Valid Data Type Can Used to Define a Member in a Structure

3. C++ Structures Data About a Student May Consist of: Last Name string
First Name string
Middle Initial char
Id Number int
Sex char
GPA float
Putting This All Together We Can Define A Structure

4. Defining A Structure Structures Require a Two Step Definition Process:
First – Define a struct Data Type That Defines the Members of the Required Structure
Second – Use the struct to Declare Variables Needed for the Program
struct Data Type Definition: struct struct-name {
type member1-name;
type member2-name; :
type memberN-name; };

5. Defining A Structure Definition Rules:
The Structure Definition Must Begin With Reserved Word – struct
Each Member Must Have a Type (the Type Can Be Different Then Other Members)
Semicolons Separate the Structure Members
Structure Definition Must End With };

6. Defining A Structure Variable
The struct Definition Only Defines a Data Type
To Use the Structure, Memory Must be Allocated Via Variable Declaration:
struct-type variable_identifier;
Where struct-type is the Structure Type Declared
Where variable identifier is a Valid Identifier Name

7. Initializing A Structure Variable
Like Other Variables Structures Can be Initialized at Declaration:
struct-type variable_identifier = {member1-value, member2-value,
….memberN-value};

8. Structure Example
struct studentRec { int idNumber; string lname; string fname; char initial; char sex; double gpa; };

9. Structure Variable Initialized studentRec stu1;
studentRec stu1 = {123456,”Sanders”,”Mark”,’S’,’M’,3.50};
idNumber
lname
fname
initial
sex
Gpa

10. Accessing Structure Data
A Structure is a Single Data Unit
Members Can Be Accessed Individually
To Access a Member Use The DOT notation:
struct variable_name.member_name
studentRec.lname = “Sanders”;
Members Can Be Used Like Any Other Variable

11. Accessing Structure Data (cont.)
More Examples
cout << “Enter student GPA: “;
cin >> stu1.gpa;
stu1.gpa = stu1.gpa + 0.5;
cout << fixed << showpoint << setprecision(2);
cout << stu1.lname << “, “ << stu1.fname << “ “ <<;
cout << stu1.gpa << endl;

12. Using Structure Data
Once You Have Data in the Structure, it Can Be Used Like Any Other Variable:
if (stu1.sex == ‘F’) {
cout << stu1.fname << ‘ ’ << stu1.lname << “ is Female.”;
cout << endl; }
if (stu1.gpa < 2.5)
cout << stu1.lname << “, ” << stu1.fname;
cout << “ is on probation.” << endl;

13. Structures As Arguments
Structures Can Be Passed as Data to Functions
If Data is to be Modified, Pass By Reference
void readStuInfo (studentRec& stu1) {
cout << “Enter student last name: “;
cin >> stu1.lname; :
cout << “Enter student GPA: “;
cin >> stu1.gpa; }

14. Arrays of Structures
Rather Than Using Parallel Arrays, we can use an Array of Structures
Does Not Violate Single Data Type Rule
Each Cell In The Array Will Hold One Structure
struct-type array_name[size];
studentRec studentList[MAX];
Declares Array to Store MAX Quantity of Structures
Each Cell Contains One Record With Six Members

15. Initializing Structure Array
Same As In The Past, Only Thing New Is the Subscript
studentRec studentList[MAX] = {
{123456,”Sanders”, “Mark”, ‘S’, ‘M’, 3.50},
{234789, “Blow”, “Joe”, ‘J’,‘M’, 2.50},
{367890, “Smith”, “Sally”, ‘S’,‘F’, 4.00} };
All Remaining Cells Are Initialized to “blank” or 0

16. Accessing Structure Array Data
Just Need To Use Subscript:
arrayName[index].member_name
studentList[1].idNumber = ;
studentList[2].gpa = studentList[3].gpa;
for (num = 0; num < MAX; num++) {
cout << studentList[num].lname << “, ” <<; cout << studentList[num].fname << endl; }

17. Access Structure Array Data (cont.)
Swapping Structures is like Swapping Any Variables:
studentRec temp;
temp = studentList[top];
studentList[top] = studentList[minPosition];
studentList[minPosition] = temp;

18. Nested Structure
A Nested Structure is a Structure that has a Member that is a Structure
Used to Organize Data, and to Allow for the Reuse of Variable Names
To Declare a Nested Structure You Must First Declare the Structure(s) that will be Nested
Once Declared the Structure can be used as Data Type for Members of Other Structures

19. Nested Structure (cont.)
struct address {
string street;
string city;
string state;
string zip; };
struct student
string lname;
string fname;
int age;
double gpa;
address campus;
address home;
student studentData;

20. Nested Structure (cont.)
Accessing Nested Structure
Need to Use Entire Name:
studentData.lname
studentData.fname
studentData.age
studentData.gpa
studentData.campus.street
studentData.campus.city
studentData.campus.state
studentData.campus.zip
studentData.home.street
studentData.home.city
studentData.home.state
studentData.home.zip

21. Nested Structure (cont.)
Arrays of Nested Structures
student studentList[MAX];
studentList[n].lname
studentList[n].fname
studentList[n].age
studentList[n].gpa
studentList[n].campus.street
“ “ “
studentList[n].campus.zip
studentList[n].home.street
studentList[n].home.zip