Program examples of c++?

/*











Basic Program File Structure and Sample Function Call











File: sum.cpp





Version: 3.1





Created: 9/24/96





Last updated: 10/20/99





Written by: Dr. C. S. Tritt











*/











#include %26lt;iostream%26gt; // Header for stream I/O.





#include %26lt;iomanip%26gt; // Header for I/O manipulators.











using namespace std;











// Function declaration (prototype) with default values.











float sum(float required_term, float optional_term = 0.0);











// Main program











int main(void)





{





// Declare variables. Some programmers like to declare their variables just





// before use. I like to declare all of mine at the top a each function.











int p; // Output numeric precision.





float a; // Units and description of a.





float b; // Units and description of b.











cout.setf(ios::showpoint); // Show decimal points. Good until explicitly changed.











cout %26lt;%26lt; "Enter the output precision (an integer): ";





cin %26gt;%26gt; p;





if (!cin)





{





cout %26lt;%26lt; "Input error. Aborting.\n";





return 1;





}





cout %26lt;%26lt; setprecision(p); // Set the precision. Good until explicitly changed.











cout %26lt;%26lt; "Enter two real numbers to be summed: ";





cin %26gt;%26gt; a %26gt;%26gt; b;





if (!cin)





{





cout %26lt;%26lt; "Input error. Aborting.\n";





return 2;





}











cout %26lt;%26lt; "Entered values: a = " %26lt;%26lt; a %26lt;%26lt; " and b = " %26lt;%26lt; b %26lt;%26lt; endl;





cout %26lt;%26lt; "So sum(a, b) = " %26lt;%26lt; sum(a, b) %26lt;%26lt; endl;





cout %26lt;%26lt; "And sum(a) = " %26lt;%26lt; sum(a) %26lt;%26lt; endl;











return 0;





}











// Define the sum function.











float sum(float x, float y)





{





// This function returns the sum of its arguments.











return (x + y);





}














this illustrates:


* Overall program structure including function declaration with default values.


* Inclusion of header files.


* Declaration of variables of built in types.


* Output formating.


* Writing to the screen (console output, i.e. cout) %26lt;%26lt; (the stream insertion operator).


* Reading from the keyboard (console in, i.e. cin) %26gt;%26gt; (the stream extraction operator).


* Simple selection structures (if statements).


* Use of functions that return values but don't change their arguments.

hawthorn