1. Structures
Structured Data types
Data abstraction
structs
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2. Data Types in C++ simple address structured integral floating
int char short long [ unsigned ] bool enum
float double long double
pointer reference
array class struct union

3. Structured Data Types simple data type
atomic values
'%' true
structured type (a.k.a. composite)
has component parts and organized structure
a collection or group of elements

4. Why Structured Types?
Group together multiple simple items in a single object.
Examples:
Entries in the campus directory
Cards: rank and suit
Library book entry
… more

5. How can we picture this?
title
author
numCopies
allTakenOut
BookRec

6. struct Declaration: Syntax
struct <Type Name> { <Data Type> <Member Name>; };

7. Example: Book Record Mini-Lib
// store information about books in library
struct BookRec // BookRec is the // type name { string title; // members string author; // must be distinct int numCopies; // within struct bool allTakenOut; };

8. MINI-Lib Program
// declare two book record variables BookRec book1, book2;
// assign values to book1
book1.title = "Walden";
book1.author = "Henry Thoreau"; book1.numCopies = 2;
book1.allTakenOut = false;

9. How can we picture this?
"Walden"
"Henry Thoreau" 2
false
book1

10. Aggregate Operations on structs
I/O NO
Assignment YES
Arithmetic NO
Comparison NO
Pass as Argument YES
by value or by reference
Return as function result YES

11. Assigning structs book2 = book1; Copies all members
An aggregate operation
operates on the data structure as a whole

12. Using struct Members Just like any other variable of their type
// add one to book1's copies book1.numCopies++;
// print message based on bool member if (book1.allTakenOut) cout << "Sorry, none available.";
// print a formatted title cout << setw(50) << book1.title;

13. Passing a struct by Value
// example call from main
// PrintOneBook (book1);
void PrintOneBook (BookRec inbook) {
cout << "Title: " << inbook.title << endl << "Author: " << inbook.author << endl << "Number of Copies: " << inbook.numCopies << endl;
if (inbook.allTakenOut) cout << "All copies are out."; else cout << "The book is available."; }

14. Passing a struct by Reference
// example call from main
// AddBooks (5, book1);
void AddBooks (int numPurchased,BookRec& thisbook) {
thisbook.numCopies = thisbook.numCopies +
numPurchased;
cout << "The library now has " << thisbook.numCopies << " copies of " << thisbook.title; }

15. Nested (hierarchical) structs
Members of a struct may be structs
When to nest structs
if nesting improves readability
if a structure is used repeatedly inside other structs
Beware: too many levels of nesting may impair readabilty

16. Example: nested structs
// add date to our library book info
struct DateRec // declare a type to represent a date { int month,
day,
year; };

17. Using DateRec struct NewBookRec {
string title, author; DateRec datePublished; int numCopies; bool allTakenOut; }; …
NewBookRec book3;

18. How can we picture this new book?
title
author }
month
book3.datePublished
day
year
numCopies
allTakenOut
book3

19. Read in Date Published
cout << "Enter the date published “ << “ as MM DD YYYY -> "; cin >> book3.datePublished.month >> book3.datePublished.day >> book3.datePublished.year;

20. Data Structures What is a data structure?
Layout of information in a program to hold whatever data it needs
Homogeneous data layout (arrays)
Heterogeneous data layout (structures)
Combinations of the two
Choosing a data structure is an important step in writing a complex program…

21. Pick a Data Structure to hold…
…the names of all the states in the USA
…the season statistical totals for a baseball player
…the service information for a car
…the daily price of a stock for the last 6 months
…the ID numbers of passengers on a plane
…the quantity of stars in each square degree of the sky
…the directory information for a University student
…the directory information for all University students