Structures
NUML Lahore Campus
Introducing Structures
A structure is a collection of multiple data types that
can be referenced with single name.
The data items in structure are called structure
members, elements, or fields.
The difference between array and structure: is that
array must consists of a set of values of same data
type but on the other hand, structure may consists
of different data types.
Defining the Structure
• Structure definition tells how Syntax:
the structure is organized: it struct StructName
specifies what members the {
DataType1 Identifier1;
structure will contain. DataType2 Identifier2;
.
.
.
Syntax & Example };
Example:
struct Product
{
int ID;
string name;
float price;
};
Structure Definition Syntax
Declaring a Structure variable
• Structure variable can be defined after the definition of a
structure. The syntax of the declaration is:
StructName Identifier;
Example:
part processor;
part keyboard;
• This declaration tells the compiler to allocate memory space
according to the elements of the structure.
• The structure variable processor and keyboard occupies 12
bytes in the memory. 4 bytes for modelnumber, 4 bytes for
Structure members in memory
4 Bytes
modelnumber
struct part
{ 4 Bytes
int partnumber
modelnumber;
int partnumber;
float cost; 4 Bytes
}; cost
Another way of Declaring a Structure variable
• You can also declare struct variables when you
define the struct. For example:
struct part
{
int modelnumber;
int partnumber;
float cost;
} part1;
These statements define the struct named part and
also declare part1 to be a variable of type part.
Examples
struct employee struct student
{ {
string firstName; string firstName;
string lastName; string lastName;
string address; char courseGrade;
double salary; int Score;
int deptID; double CGPA;
};
} s1, s2;
employee e1;
Initializing Structure Variables
• The syntax of initializing structure is:
StructName struct_identifier = {Value1, Value2, …};
Structure Variable Initialization with Declaration
struct student
{
string firstName;
string lastName;
char courseGrade;
int marks;
};
void main( )
{
student BC022010= {“M”, “Umar”, ‘A’, 94} ;
}
Note: Values should be written in the same sequence in which
they are specified in structure definition.
Assigning Values to Structure Variables
• After creating structure variable, values to structure
members can be assigned using dot (.) operator
• The syntax is as follows:
student BC111017;
BC111017.firstName = “Muhammad”;
BC111017.lastName = “Umar”;
BC111017.courseGrade = ‘A’;
BC111017.marks = 93;
Assigning Values to Structure Variables
• After creating structure variable, values to structure
members can be assigned using cin.
• Output to screen using cout
student BC012311;
cin>>BC012311.firstName;
cin>>BC012311.lastName;
cin>>BC012311.courseGrade;
cin>>BC012311.marks ;
Assigning one Structure Variable to another
• A structure variable can be assigned to another
structure variable only if both are of same type
• A structure variable can be initialized by assigning
another structure variable to it by using the assignment
operator as follows:
Example:
studentType newStudent = {“John”, “Lee”, ‘A’, 99} ;
studentType student2 = newStudent;
Array of Structures
• An array can also be created of user-defined type such as: structure.
• An array of structure is a type of array in which each element
contains a complete structure.
struct Book
{
int ID;
int Pages;
float Price;
};
Book NUMLLibrary[100]; // declaration of array of structures
NUMLLibrary[0]
ID Pages Price
NUMLLibrary[1]
ID Pages Price
… NUMLLibrary[99]
ID Pages Price
Initialization of Array of Structures
struct Book
{
int ID;
int Pages;
float Price;
};
Book b[3]; // declaration of array of structures
• Initializing can be at the time of declaration
Book b[3] = {{1,275,70},{2,600,90},{3,786,100}};
• Or can be assigned values using cin:
cin>>b[0].ID ;
cin>>b[0].Pages;
cin>>b[0].Price;
Array as Member of Structures
• A structure may also contain arrays as members.
struct Student
{
int RollNo;
float Marks[3];
};
• Initialization can be done at time of declaration:
Student S = {1, {70.0, 90.0, 97.0} };
Array as Member of Structures
• Or it can be assigned values later in the program:
Student S;
S.RollNo = 1;
S.Marks[0] = 70.0;
S.Marks[1] = 90.0;
S.Marks[2] = 97.0;
• Or user can use cin to get input directly:
cin>>S.RollNo;
cin>>S.Marks[0];
cin>>S.Marks[1];
cin>>S.Marks[2];
Nested Structure
• A structure can be a member of another structure:
called nesting of structure
struct A
{
int x;
double y;
};
struct B
{ record
char ch; v1
A v1; ch x y
};
B record;
Initializing/Assigning to Nested Structure
struct A{ void main()
int x; {
float y; B record;
}; cin>>record.ch;
cin>>record.v2.x;
struct B{ cin>>record.v2.y;
char ch; }
A v2;
}; void main()
{
B record;
void main() record.ch = ‘S’;
{ record.v2.x = 100;
B record = {‘S’, {100, 3.6} }; record.v2.y = 3.6;
} }
Class Exercises(1) – Find Errors
• Find errors:
struct
{
int x;
float y;
};
struct values
{
char name[20];
int age;
}
Class Exercises(2) – Find Errors
• Find errors:
struct TwoVals
{
int a,b;
};
int main()
{
TwoVals.a=10;
TwoVals.b=20;
}
Class Exercises(3) – Find Errors
• Find errors:
struct ThreeVals
{
int a,b,c;
};
int main()
{
ThreeVals vals={1,2,3};
cout<<vals<<endl;
return 0;
}
Class Exercises(4) – Find Errors
• Find errors:
struct names
{
char first[20];
char last[20];
};
int main()
{
names customer = {“Muhammad”, “Ali”};
cout<<names.first<<endl;
cout<<names.last<<endl;
return 0;
}
Class Exercises(5) – Find Errors
• Find errors:
struct TwoVals
{
int a=5;
int b=10;
};
int main()
{
TwoVals v;
cout<<v.a<<“ “<<v.b;
return 0;
}
An Array of Structures
• We can also make an array of structures. Suppose we need to store the data of 100
students. Declaring 100 separate variables of the structure is definitely not a good
option. For that, we need to create an array of structures.
• Let's see an example for 5 students.
Next Slide
Example: An Array of Structures
Class Exercise-6
• Define a structure called “car”. The member elements
of the car structure are:
• string Model;
• int Year;
• float Price
Create an array of 30 cars. Get input for all 30 cars
from the user. Then the program should display
complete information (Model, Year, Price) of those
cars only which are above 500000 in price.
Class Exercise-6
Class Exercise-7
• Write a program that implements the following using C++
struct. The program should finally displays the values stored
in a phone directory (for 10 people)
PhoneDirectory
Name PhoneNo Address
City Country
Class Exercise-7
