1. Simplest program and Data Output Sen Zhang

2. The simplest program looks like a single person company! void main() { // this starts a comment line // here is where you put your code… } One function, with a head and the empty body

3. The simplest program looks like a single person company! int main() { // this starts a comment line // here is where you put your code… return 0; } One function, with a head and the empty body

4. Why main needs to return a value ? DOS command to determine the return code is ERRORLEVEL, most people use the name errorlevel. Errorlevels are not a standard feature of every command. A certain errorlevel may mean anything the programmer wanted it to. Most programmers agree that an errorlevel 0 means the command executed succesfully, and an errorlevel 1 or higher usually spells trouble. But there are many exceptions to this general rule. int main() { return 11.9; } c:\sen\t1222\Debug>echo %errorlevel% 0 c:\sen\t1222\Debug>t1222 c:\sen\t1222\Debug>echo %errorlevel% 11

5. 5 The cout Object The cout object represents the standard output display device, so anything you insert into cout will reflect on the standard output display device. – The display device is usually a video screen – Name derived from Console OUTput and pronounced “see out” Data is passed to cout by the insertion symbol cout << “Hello there, World!”;

6. 6 C++ Sample Code using cout

7. 7 Preprocessor Command Performs an action before the compiler translates source code to machine code – An example is: #include – Causes the iostream file to be inserted wherever the #include command appears iostream is part of the C++ standard library – Included in iostream are two important classes: istream : Declarations and methods for data input ostream : Declarations and methods for data output

8. 8 Namespaces Files accessed by compiler when looking for prewritten classes or functions Sample namespace statement: – using namespace std; – iostream contained in a namespace called std – Compiler uses iostream’s cout object from std whenever cout is referenced

9. 9 More C++ Sample Code

10. 10 More C++ Sample Code (continued)

11. #include using namespace std; int main() { cout<<"hi!"; cout<<endl; cout<<3+5; cout<<endl; cout<<"3+5"; return 0; }

12. 12 Formatted Output Read book, page 53 to 66 Besides displaying correct information, a program must present results attractively. Field width manipulators: control format of numbers displayed by cout – Manipulators included in the output stream

13. Output manipulators Output manipulators are items used to manipulate how the output stream of characters is displayed.

14. Manipulators for columnizng styles setw(n) setfill(‘c’)

15. When a manipulator requiring an argument is used, the iomanip header file must be included as part of the program. This is accomplished by the preprocessor command #include.

16. Setw(width) The setw(width) manipulator included in the stream of data passed to cout is used to set the displayed field width. The width in this manipulator should be replaced by a concrete integer number say 10. It will reserves a field with a width of 10 for any subsequent number in the stream.

17. Setfill(symbol) Set the default fill character to x. (The default fill character is a space) It will use the symbol to fill out the space that has not been used by the data.

18. Special manipulators for numbers fixed setprecision(n)

19. fixed Always show a decimal point and use a default of 6 digits after the decimal point. Fill with trailing zeros, if necessary.

20. setprecision(number) Set the floating-point precision to the places of number. If the fixed manipulator is designated, number specifies the total number of displayed digits after the decimal point; otherwise, it specifies the total number of significant digits displayed (both integer portion and fractional portion)

21. 21 Formatted Output (continued)

22. 22 Formatted Output (continued)

23. Links to several lists of basic C++ constructs A list of keywords A list of operators, with associativity of each and precedence among them. A list of operators, with associativity of each and precedence among them. A list of io flags and format manipulators A c++ reference website Literals Tokens identifiers 23