1. A “User – Defined Data Type”
Creating Structures
A “User – Defined Data Type”

2. Structure Concepts Structures use the reserved word struct
Structures are defined just after
using namespace std;
and before function prototypes

3. Structure Concepts (cont’d)
Structures package related data together
Ex. Description, price, quantity
might be combined to represent an item in a store
Syntax:

4. Structure Concepts (cont’d)
Remember – for all practical purposes a structure is a data type so the structure identifies can not be used as a variable.
Variables of the structure data type have to be created
Example - name a_name;
item an_item;

5. Use of “dot notation”
Dot notation is used to identify the data member to be accessed.
Example - getline(cin, a_name.first);
cout << “price: “<< an_item.price;
Data members can be used just like standard variables of the same data type –
tot_value = an_item.price * an_item.qoh;

6. Structure Declaration and Initialization
To declare a variable of a structure type and initialize it – a data set has to be used. Braces are used to define the data set. Example - name a_name = {“XX”, “XX”, “XX”}; item block={“cheek”, 5, 45.50}; Let’s say the price of the block increased by 30%. We could now do something like – block.cost = block.cost * 1.3;

7. If we just sold 3 blocks we could – block.qoh = block.qoh – 3;
Another example – We want to print out the data in a_name in the form of last name, first name then middle name –
cout << a_name.last<<“, “<<a_name.first
<<“ “<<a_name.mi<< endl;
So we have packaged data together into a single data unit – a data structure.

8. Now the Huge Advantage
Remember the structure variable is a SINGLE value that has several components that can be accessed.
Remember that a function can return only a single value which is created (or modified) within the function

9. Assume the following function heading – name make_name( ) This function is going to return a single value of name type – remember that each name variable has 3 parts (refer to slide 3) packaged into a single name

10. So we might define the make_name function below –
name make_name ( ) {
name a_name;
cout << “First name: “;
getline(cin, a_name.first);
cout << “Last name: “;
getline(cin, a_name.last);
cout << “Middle name: “;
getline(cin, a_name.mi);
return a_name;
}//End of name make_name ( )