1. Glenn Stevenson CSIS 113A MSJC
CSIS 113A Lecture 13
Structures
Glenn Stevenson CSIS 113A MSJC

2. Glenn Stevenson CSIS 113A MSJC
What Is A Structure
An abstract data type that the programmer defines
You have used int, char, float, etc
Now you can create your own type
Person, BankAccoun, etc
Precursor to creating classes
Understanding structures goes a long way to helping you understand classes
Glenn Stevenson CSIS 113A MSJC

3. Glenn Stevenson CSIS 113A MSJC
Defining a structure
myStruct is a newly defined type it does not occupy any space You have to create an instance of it!
Glenn Stevenson CSIS 113A MSJC

4. Glenn Stevenson CSIS 113A MSJC
Creating an Instance
int variable x is created
myStruct variables y, aStruct are created
Glenn Stevenson CSIS 113A MSJC

5. Accessing Member Variables
You access member variables using the . (dot) operator
Glenn Stevenson CSIS 113A MSJC

6. Glenn Stevenson CSIS 113A MSJC
An Example
#include <iostream> #include <ctime> using namespace std;
struct TIME { int hour; int minute; int second; };
int main() { TIME t; int hour;
   cout << "Enter hour, minute, second " << endl;    cin >> t.hour >> t.minute >> t.second;    hour = t.hour;    if(hour > 12) //Convert military hour to standard time       hour-=12;
    cout << "The time you entered is " << hour << ":" << t.minute << ":" << t.second << endl; }
Glenn Stevenson CSIS 113A MSJC

7. Initializing At Declaration
struct TIME { int hour; int minute; int second; };
Glenn Stevenson CSIS 113A MSJC

8. Glenn Stevenson CSIS 113A MSJC
Example
#include <iostream> #include <ctime> using namespace std;
struct TIME { int hour; int minute; int second; };
int main() { TIME t = {12,20,22};
cout << "The is " << t.hour << ":" << t.minute << ":" << t.second << endl; }
Glenn Stevenson CSIS 113A MSJC

9. Passing Structures To Functions
Pass Structures that same way you do any other variable
Can pass by pointer, reference, value
Glenn Stevenson CSIS 113A MSJC

10. Glenn Stevenson CSIS 113A MSJC
ByValue
#include <iostream> #include <ctime> using namespace std;
void printTime(TIME tm);
int main() { TIME t = {12,20,22}; printTime(t); }
void printTime(TIME tm) {
cout << "The is " << tm.hour << ":" << tm.minute << ":" << tm.second << endl;
Glenn Stevenson CSIS 113A MSJC

11. Glenn Stevenson CSIS 113A MSJC
ByReference
#include <iostream> #include <ctime> using namespace std;
void printTime(TIME &tm);
int main() { TIME t;
getTime(t); cout << t.hour << “ “ << t.minute << “ “ << t.second << endl; return 0; }
void getTime(TIME &tm) { tm.hour = 12; tm.minute = 30; tm.second = 25;
Glenn Stevenson CSIS 113A MSJC

12. Glenn Stevenson CSIS 113A MSJC
Pass By Pointer
Passing by pointer is a little different
When dealing with a pointer to a structure, you don’t use the dot operator
Instead you use the arrow operator
->
A dash followed by greater than
Glenn Stevenson CSIS 113A MSJC

13. Glenn Stevenson CSIS 113A MSJC
By Pointer
#include <iostream> #include <ctime> using namespace std;
void printTime(TIME *tm);
int main() { TIME t;
getTime(&t); cout << t.hour << “ “ << t.minute << “ “ << t.second << endl; return 0; }
void getTime(TIME *tm) { tm->hour = 12; tm->minute = 30; tm->second = 25;
Glenn Stevenson CSIS 113A MSJC

14. Glenn Stevenson CSIS 113A MSJC
Structure & Arrays
Handled Just Like any other type array!
Glenn Stevenson CSIS 113A MSJC

15. Glenn Stevenson CSIS 113A MSJC
Accessing The Data
You use the subscript operator
Glenn Stevenson CSIS 113A MSJC

16. Initialization At Declaration
Just like any other array
Watch your braces
Glenn Stevenson CSIS 113A MSJC

17. Glenn Stevenson CSIS 113A MSJC
Example
#include <iostream> #include <ctime> using namespace std;
struct TIME { int hour; int minute; int second; };
int main() { TIME t[3] = {    {12,20,22},    {1,10,12},    {5,15,0}, };
   for(int i = 0; i < 3; i++)       cout << "The time is " << t[i].hour << ":" << t[i].minute << ":" << t[i].second << endl; }
Glenn Stevenson CSIS 113A MSJC

18. Passing Arrays to Functions
Just like any other array
void printArray(TIME time[], int size); void fillArray(TIME time[], int size);
int main() {    fillArray(t,3);    printArray(t, 3); }
void fillArray(TIME Time[], int size) {
    srand(time(0));     for(int i = 0; i < size; i++)    {        Time[i].hour = rand() % 13;        Time[i].second = rand() % 61;        Time[i].minute = rand() % 61;    }
Glenn Stevenson CSIS 113A MSJC