1. MIS 120
Structures

2. The Problem
Recall that elements of arrays must all be of the SAME type.
In some cases, we want to group elements of DIFFERENT types.
scores :
employee R. Jones 123 Elm 6/12/55 $14.75

3. Solving with Parallel Arrays
We learned in Chapter 11 that one way to solve this problem is with parallel arrays.
While parallel arrays will solve the problem, they are inefficient and put a heavy burden on the developer and QA. 1 2 3 4 5
Student Name
Jeff
Joey
Susan
Joanne
Dhale
Becky
Exam 1 Grade
104 78 92 84 52 87
Exam 2 Grade
128 91 88
110 40
115

4. Records
RECORDS are used to group related components of different types
Components of the record are called fields
In C++
record called a struct (structure)
fields called members

5. Solving with a Struct C++ struct structured data type
fixed number of components
elements accessed by name, not by index
components may be of different types
struct partStruct { string descrip, partNum; float unitPrice; int qty; };

6. Declaring Struct Variables
Given
Declare
Use
struct partStruct { string descrip, partNum; float unitPrice; int qty; };
partStruct myPart;
myPart.descrip = “Tire”;
myPart.unitPrice = 55.25;
cout << myPart.descrip << “are $” << myPart.unitPrice << “each.”;

7. Use within Functions A struct variable can be passed as a parameter
Can be passed by value or by reference.
A function can return a value of the type struct

8. Some Limitations No aggregate Input/Output operations
Data must be read one member at a time
Contents must be written one member at a time.
Compares must be done one member at a time
if(student.firstName == newStudent.firstName &&
student.lastName == newStudent.lastName) ...

9. The True Power of Structs!
You can declare an Array of Structs!
First declare a struct (such as partStruct)
Then specify an array of that type
You can then access any member within the array
partStruct partList [50];
for (x = 0; x <50; x++) cout << partList[x].descrip;

10. Questions?