// This program demonstrates some basic programming
// techniques in C++.  Besides being lecture notes,
// it is also a fully functioning program which you
// may load into Visual C++, compile, and run.

// How to specify your #include's

#include <iostream.h>
#include <stdio.h>

// How to specify your main function

void main()
{
 // How to declare an integer

 int x;

 // How to declare multiple integers

 int y,z;

 // How to declare a floating point number

 double w;

 // How to set the value of a variable

 x = 25;

 w = 25.2542342;

 // More complex arithmetic expressions

 y = 3*x*x - 2*x + 17;
 z = (y - 42) / (x + 17);

 // How to print out a message (endl == end of line)

 cout << "This will print out a message." << endl;

 // How to print out a variable value

 cout << x << endl;

 // How to print out a message and a variable value

 cout << "The value of x is " << x << endl;

 // How to read in a variable value

 cin >> y;

 // How to read in a variable value with a prompt
 // (note:  do not use "endl"):

 cout << "Please enter a number (0 to exit): ";
 cin >> y;

 // How to write a simple conditional ("if") statement

 if (x < y)
 {
  // This code is only called if x < y
  cout << x << " is less than " << y << endl;
 }

 // How to write a conditional with an else statement

 if (x < y)
 {
  // This code is only called if x < y
  cout << x << " is less than " << y << endl;
 }
 else
 {
  // This code is only called if x >= y
  cout << x << " is not less than " << y << endl;
 }

 // How to test for equality in a conditional

 if (x == y)
 {
  // This code is only called if x equals y
  cout << x << " equals " << y << endl;
 }

 // How to test for inequality in a conditional

 if (x != y)
 {
  // This code is only called if x does not equal y
  cout << x << " does not equal " << y << endl;
 }

 // How to test for both of two conditions (logical AND)

 if ((x < y) && (y > 2))
 {
  // This code is only called if x > y
  // *AND* y > 2
  cout << "x>y and y>2" << endl;
 }

 // How to test for either of two conditions (logical OR)

 if ((x < y) || (y > 2))
 {
  // This code is only called if x > y
  // *OR* y > 2
  cout << "x>y or y>2" << endl;
 }

 // How to test for the negation of a condition (logical NOT)

 if (!(x < y))
 {
  // This code is only called if it is *not* true
  // that x < y (that is, if x >= y)
  cout << "x is not less than y" << endl;
 }

 // How to loop using WHILE

 x = 10;
 y = 0;
 while (y < x)
 {
  // This code is called repeatedly until it is
  // NOT true that y < x
  cout << "y = " << y << endl;
  y = y + 1;
 }

 // How to not exit the program until the user
 // hits the Enter key

 cout << "Please hit Enter to exit the program." << endl;
 getchar();

 // How to exit the main() function immediately:  return
 if (x <= 0)
 {
  // This code is only called if x <= 0
  // It uses "return" to immediately exit the main() function
  return;
 }
}