1 / 26

Introduction to Computer Science

Introduction to Computer Science. COMP 51 – Fall 2012 – Section 2. Structures. Business. Exam 2 next week (Review on Wed) Office hours will be next Thurs instead of Tues Project 5 – Part A Will discuss briefly on Monday Due Monday, Nov 26 th

liseli
Download Presentation

Introduction to Computer Science

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Introduction to Computer Science COMP 51 – Fall 2012 – Section 2 Structures

  2. Business • Exam 2 next week (Review on Wed) • Office hours will be next Thurs instead of Tues • Project 5 – Part A • Will discuss briefly on Monday • Due Monday, Nov 26th • Also on Monday, you will complete Lab 8 (which we will start today). I will be in class until noon (at which time I have to leave for a meeting)

  3. Structures

  4. Structures • Prior knowledge – Arrays • Collection of multiple values of the same type • New concept – Structures • Collection of multiple values of different types • Treated as a single item, like arrays • Several key differences • Structure elements are accessed by name, not by index number • Must first define structure prior to declaring any variables

  5. Why Structures? • The pieces of data are related in some way • Easier to keep them together (all in one place) • Easier to move them around all at once! • Examples • Certificate of Deposit at a bank • Account balance, interest rate, term length • Time of day • Hour, minute, second • Student information record • First name, last name, student ID number, cell phone, home phone, campus phone, etc…

  6. New Keyword: struct • The keyword struct is used to create a new structure • Each item (member) inside the structure has a name, just like a variable • Two (or more) names to keep track of now • The name of the structure type • The name(s) of elements inside the structure

  7. Define Structure Type • Define struct globally (typically) • Example for certificate of deposit account • Name of structure? • CDAccount • Name of members in the structure? • balance, InterestRate, term structCDAccount{ double balance; double interestRate;intterm;};

  8. Declare Structure Variable • Step 1: Definestructure type (previous slide) • Compiler then knows what a “CDAccount” is • Step 2: Declare a variable with this new structure type • Just like declaring an int, float, char, … • Variable account of type CDAccount • It contains “member variables” CDAccount account;

  9. Accessing Structure Members • Individual elements are called “member variables” • Different structure types can have same member variable names without conflict • New operator to access members: . • Use to read or write a member variable A period! “dot” account.balance account.interestRate account.term

  10. Structures as Function Arguments • Passed like any simple data type • Pass-by-value or Pass-by-reference • Neat trick: Easily pass multiple data items to a function! • Can also be returned by function • Return type is structure type • Neat trick: Easily return multiple data items from a function!

  11. Example Program #include <iostream> using namespace std; // Structure for certificate of deposit structCDAccount { double balance; double interestRate; int term; }; CDAccountopenAccount(void); void printAccount(CDAccount account); Function returning a struct Function taking a struct

  12. Example Program intmain(void) { CDAccount account; account = openAccount(); printAccount(account); return 0; } Declare a new instance of the CDAccount structure called “account”

  13. Example Program CDAccountopenAccount(void) { CDAccount account; cout << "Enter account balance: $"; cin >> account.balance; cout << "Enter account interest rate in %: "; cin >> account.interestRate; cout << "Enter number of months until maturity: "; cin >> account.term; return account; } Returns the variable account, which is a structure of type CDAccount and contains 3 member variables (balance, interestRate, and term)

  14. Example Program void printAccount(CDAccount account) { double rateFraction, interestEarned, endBalance; rateFraction = account.interestRate/100.0; interestEarned = account.balance* (rateFraction*(account.term/12.0)); endBalance = interestEarned + account.balance; cout << "When your CD matures in " << account.term << " months, it will have a balance of $" << endBalance << endl; }

  15. Example Output Enter account balance: $100.00 Enter account interest rate in %: 10.0 Enter number of months until maturity: 6 When your CD matures in 6 months, it will have a balance of $105

  16. Pitfall – Required Semicolon! • Semicolon after structure definition is required! • structWeatherData{ double temperature; double windVelocity;};  semicolon! • Required since you can declare structurevariables in this location

  17. Pitfall – Initialization • Member variables cannot be initialized in the declaration • The structure definition only defines the types, names and order of members • structWeatherData{ double temperature = 32.0; double windVelocity = 10;}; This is not allowed

  18. Uniqueness of Names • Different structures may use the same member variables names without confusion • Names within a structure still have to be unique, however structCDAccount{ double balance; double interestRate;int term;}; structCheckingAccount{ double balance; double interestRate;};

  19. Structure Assignments • An entire structure can be copied in a single statement (in contrast to arrays, which must be element by element) • Declare two structure variables • CDAccount account1;CDAccount account2;// Set data in account1account2 = account1; • Simply copies each member variable from applesinto member variables from oranges • Can’t do anything else, however  • No comparisons (==, >, <, etc.) • At least not without extra programming work…

  20. Arrays of Structures • An array of 10,000 CD account structures • CDAccount accounts[10000]; • Accessing an element of the structure in the array • cout << “Account #10 balance is $” << accounts[10].balance << endl; • Structures can have elements that are arrays, too

  21. Lab 8: Structures Exercise

  22. Lab 8 • You’re going to create a program to store information about a team of fencers at a tournament. • Create a Fencer structure to store the first name, weapon and scores from 2 bouts for each fencer. There are three possible weapons: “foil”, “epee” and “saber”. The scores for a bout are integers between 0 and 15.

  23. Lab 8 • Create an array of 5 Fencers. This array should be declared in main(). You will pass it to functions that use it. (Remember that arrays are always passed by reference to functions). • Create a function to prompt the user for information about each fencer and fill it into the array • getTeam(Fencer team[], intteamSize); • Create a function to print out the name, weapon and highest score of each fencer on the team. • printTeam(Fencer team[], intteamSize);

  24. Lab 8 • Create a function to ask the user to select a weapon and then print out the names of all the fencers who use that particular weapon. • weaponChoice(Fencer team[], intteamSize); • Call these three functions in sequence inside main().

  25. Lab 8 Sample input and output

  26. Questions? ? ? ?

More Related