1. Introduction to cout / cin

2. Purpose
cout is used to print to the screen in a C++ Console Application. cin is used to read user input from the keyboard in a C++ Console Application.

3. #includes
cout and cin are defined by the C++ standard library iostream. To use these utilites: #include <iostream> Additional utilities for formatting cout are in: #include <iomanip>

4. Basic Idea
cout is a stream from the application (executing in memory) to the screen. Characters are inserted into the stream and “fall out” on the screen. I/O manipulations may be used to format the characters before they are written.

5. Basic Idea
cout is a stream from the application (executing in memory) to the screen. Characters are inserted into the stream and “fall out” on the screen. I/O manipulations may be used to format the characters before they are written.

6. Basic Idea

7. Basic Idea

8. cout syntax
cout << expression; where expression is a literal, variable or more complex expression that evaluates to one value.

9. cout syntax
cout << expr1 << expr2 << ... << exprn; is equivalent to: cout << expr1; cout << expr2; ... cout << exprn;

10. cout style
Can vary greatly depending on the situation. Make it clear to another programmer and easy to maintain.

11. cout style
Good style: cout << ” \n”; cout << ”| Hello |\n”;

12. cout style
Good style: cout << ” \n” << ”| Hello |\n” << ” \n”;

13. cout style
Poor style:
cout << ” \n| Hello |\n \n”;

14. iomanip Floating Point Numbers:
// print floats/doubles in decimal format with
// 2 digits past the decimal point.
// Prints nothing. In effect until changed.
cout << fixed << setprecision(2);

15. iomanip Field Widths: cout << setw(10) << ”Hello”;
// set total field with of a value
cout << setw(10) << ”Hello”;
Prints 5 spaces then 5 characters:
Hello

16. iomanip Field Widths: Prints 5 spaces then 5 characters then There
// effect is only for 1 value
cout << setw(10) << ”Hello” << ”There”;
Prints 5 spaces then 5 characters then There
HelloThere

17. Basic Idea
cin is a stream from the keyboard to the console application (executing in memory) Characters are inserted into the stream by the user and are extracted by cin.

18. Basic Idea

19. cin Syntax: (simple) Semantics: in general cin >> variable;
Read as:
variable = whatever is entered by the user;

20. cin Semantics: in general - halts execution of the program
- the user enters data and presses ENTER
- the data is converted to the data type of the
variable.
- the data entered is stored in the variable
- execution continues

21. cin Semantics: specifically Exactly how cin behaves depends on the:
- data type of the variable
- what is currently in "the stream", if anything.
- data type of the data entered by the user

22. More Details Coming Soon!
cin
More Details Coming Soon!
For now, assume that for each cin:
- the user enters the correct data type
- the user enters NO SPACES/TABS/etc
- the user presses ENTER when done

23. cin examples

24. cin examples

25. cin examples