listing 1
/* Program #1 - A first C++ program.

   Enter this program, then compile and run it.
*/

#include <iostream>
using namespace std;

// main() is where program execution begins.
int main()
{
  cout << "This is my first C++ program.";

  return 0;
}

listing 2
/* Program #1 - A first C++ program.

   Enter this program, then compile and run it.
*/

listing 3
#include <iostream>

listing 4
using namespace std;

listing 5
// main() is where program execution begins.

listing 6
int main()

listing 7
cout << "This is my first C++ program.";

listing 8
return 0;

listing 9
#include <iostream.h>

listing 10
using namespace std;

listing 11
#include <iostream>
using namespace std;

listing 12
#include <iostream.h>

listing 13
// Program #2 - Using a variable

#include <iostream>
using namespace std;

int main()
{
  int value; // this declares a variable

  value = 1023; // this assigns 1023 to value

  cout << "This program prints the value: ";
  cout << value; // This displays 1023

  return 0;
}

listing 14
int value;  // this declares a variable

listing 15
value = 1023; // this assigns 1023 to value

listing 16
cout << value; // This displays 1023

listing 17
// This program converts gallons to liters.

#include <iostream>
using namespace std;

int main()
{
  int gallons, liters;

  cout << "Enter number of gallons: ";
  cin >> gallons; // this inputs from the user

  liters = gallons * 4; // convert to liters

  cout << "Liters: " << liters; 

  return 0;
}

listing 18
cin >> gallons; // this inputs from the user

listing 19
cout << "Liters: " << liters;

listing 20
/* This program converts gallons to liters using
   floating point numbers. */

#include <iostream>
using namespace std;

int main()
{
  float gallons, liters;

  cout << "Enter number of gallons: ";
  cin >> gallons; // this inputs from the user

  liters = gallons * 3.7854; // convert to liters

  cout << "Liters: " << liters; 

  return 0;
}

listing 21
/* This program contains two functions: main()
   and myfunc().
*/
#include <iostream>
using namespace std;

void myfunc(); // myfunc's protoype

int main()
{
  cout << "In main()";
  myfunc(); // call myfunc()
  cout << "Back in main()";

  return 0;
}

void myfunc()
{
  cout << " Inside myfunc() ";
}

listing 22
void myfunc(); // myfunc's prototype

listing 23
// Use the abs() function.
#include <iostream>
#include <cstdlib> // for older compilers, use <stdlib.h>
using namespace std;

int main()
{
  cout << abs(-10);

  return 0;
}

listing 24
void mul(int x, int y)
{
  cout << x * y << " ";
}

listing 25
// A simple program that demonstrates mul(). 

#include <iostream>
using namespace std;

void mul(int x, int y); // mul()'s prototype

int main()
{
  mul(10, 20);
  mul(5, 6);
  mul(8, 9);

  return 0;
}

void mul(int x, int y)
{
  cout << x * y << " ";
}

listing 26
// Returning a value.

#include <iostream>
using namespace std;

int mul(int x, int y); // mul()'s prototype

int main()
{
  int answer;

  answer = mul(10, 11); // assign return value
  cout << "The answer is " <<  answer;

  return 0;
}

// This function returns a value. 
int mul(int x, int y)
{
  return x * y; // return product of x and y
}

listing 27
// An old-style way to code mul().
mul(int x, int y) // default to int return type
{
  return x * y; // return product of x and y
}

listing 28
/* This program demonstrates the \n code, which
   generates a new line.
*/
#include <iostream>
using namespace std;

int main()
{
  cout << "one\n";
  cout << "two\n";
  cout << "three";
  cout << "four";

return 0;
}

listing 29
if(10 < 11) cout << "10 is less than 11";

listing 30
if(10==11) cout << "hello";

listing 31
// This program illustrates the if statement.

#include <iostream>
using namespace std;

int main()
{
  int a, b;

  cout << "Enter first number: ";
  cin >> a;
  cout << "Enter second number: ";
  cin >> b;

  if(a < b) cout << "First number is less than second.";

  return 0;
}

listing 32
// A program that illustrates the for loop.

#include <iostream>
using namespace std;

int main()
{
  int count;

  for(count=1; count<=100; count=count+1) 
    cout << count << " ";

  return 0;
}

listing 33
for(count=1; count<=100; count++)
  cout << count << " ";

listing 34
if(x<10) {
  cout << "too low, try again";
  cin >> x;
}

listing 35
// This program demonstrates a block of code.

#include <iostream>
using namespace std;

int main()
{
  int a, b;

  cout << "Enter first number: ";
  cin >> a;
  cout << "Enter second number: ";
  cin >> b;

  if(a < b) {
    cout << "First number is less than second.\n";
    cout << "Their difference is: " << b-a;
  }

  return 0;
}

listing 36
x = y;
y = y+1;
mul(x, y);

listing 37
x = y;  y = y+1;  mul(x, y);