C++ Tutorial/Data Types/float

cin handles double and float type values

<source lang="cpp">#include <iostream> using namespace std; int main() {

  int myInt;
  long myLong;
  double myDouble;
  float myFloat;
  unsigned int myUnsigned;
  cout << "int: ";
  cin >> myInt;
  cout << "Long: ";
  cin >> myLong;
  cout << "Double: ";
  cin >> myDouble;
  cout << "Float: ";
  cin >> myFloat;
  cout << "Unsigned: ";
  cin >> myUnsigned;
  cout << "\n\nInt:\t" << myInt << endl;
  cout << "Long:\t" << myLong << endl;
  cout << "Double:\t" << myDouble << endl;
  cout << "Float:\t" << myFloat << endl;
  cout << "Unsigned:\t" << myUnsigned << endl;
  return 0;

}</source>

constant floats, floating point variables

<source lang="cpp">#include <iostream> using namespace std;

int main(){

  float rad;                        
  const float PI = 3.14159F;        
 
  cout << "Enter radius of circle: ";
  cin >> rad;                        
  float area = PI * rad * rad;         
  cout << "Area is " << area << endl;
  return 0;   

}</source>

Define function whose parameter and return value are both float

<source lang="cpp">#include <iostream> using namespace std; float cube_number(float num); int main() {

 float number;
 float number3;
 cout << "Please enter a number \n";
 cin >> number;
 
 number3 = cube_number(number);
 cout << number << " cubed is " << number3;
 return 1; 

} float cube_number(float num) {

 float answer;
 answer = num * num * num;
 return answer;

}</source>

Please enter a number
123
123 cubed is 1.86087e+006"

Display decimal and float with format

<source lang="cpp">#include <iostream>

1. include <iomanip>

using namespace std; int main() {

  cout << 2002 <<endl;
  cout << "In hex " << hex<< 2002 <<endl;
  cout.setf(ios::scientific,ios::floatfield);
  cout <<987.123456 <<endl;
  cout << setprecision(3) << 987.123456 <<endl;
  cout.fill("X");
  cout.width(10);
  cout << 1234 <<endl;
  cout.setf(ios::left,ios::adjustfield);
  cout.width(10);
  cout << 1234 <<endl;
  return 0;

}</source>

float number array

<source lang="cpp">#include <iostream> float data[5]; // data to average and total float total; // the total of the data items float average; // average of the items int main() {

   data[0] = 34.0;
   data[1] = 27.0;
   data[2] = 46.5;
   data[3] = 82.0;
   data[4] = 22.0;
   total = data[0] + data[1] + data[2] + data[3] + data[4];
   average =  total / 5.0;
   std::cout << "Total " << total << " Average " << average << "\n";
   return (0);

}</source>

Total 211.5 Average 42.3

float point constant number

<source lang="cpp">#include <iostream.h> const float PI = 3.1415926; inline float Area(const float r); main() {

  float radius = 2.9;
  cout << "The Area is " << Area(radius) << "\n";

} float Area(const float r){

   return PI * r * r;

}</source>

The Area is 26.4208

Local Float Variables and Parameters: convert the temperature in Fahrenheit to Celsius

<source lang="cpp">#include <iostream> float Convert(float); int main() {

  using namespace std;
  float TempFer = 100.00;
  float TempCel;
  TempCel = Convert(TempFer);
  cout << TempCel << endl;
  return 0;

} float Convert(float TempFer) {

  float TempCel;
  TempCel = ((TempFer - 32) * 5) / 9;
  return TempCel;

}</source>

Read float point numbers from keyboard and save them to a float array

<source lang="cpp">#include <iostream> using namespace std;

   int main()
   {
       float temp[5];
       cout << "float number \n";
       cin >> temp[0];
       cout << "float number \n";
       cin >> temp[1];
       cout << "float number \n";
       cin >> temp[2];
       cout << "float number \n";
       cin >> temp[3];
       cout << "float number \n";
       cin >> temp[4];
       cout << temp[0] << ", " << temp[1] << ", "<< temp[2] <<      ", "<< tem

p[3] << ", ";

       cout << temp[4] << endl; 
    return 0;
 }</source>

float number
123.123
float number
.123.123
float number
float number
123.123.
float number
123.123, 0.123, 0.123, 123.123, 7.93782e+033

Tests whether two floating-point numbers are approximately equal.

<source lang="cpp">#include <iostream>

1. include <algorithm>
2. include <cmath>

using namespace std; bool approx_equal(double x, double y) {

  const double EPSILON = 1E-14;
  if (x == 0) return fabs(y) <= EPSILON;
  if (y == 0) return fabs(x) <= EPSILON;
  return fabs(x - y) / max(fabs(x), fabs(y)) <= EPSILON;

} int main() {

  double x;
  cout << "Enter a number: ";
  cin >> x;
  double y;
  cout << "Enter another number: ";
  cin >> y;
  if (approx_equal(x, y))
     cout << "The numbers are approximately equal.\n";
  else
     cout << "The numbers are different.\n";
  return 0;

}</source>

Type Conversion: from float to double

<source lang="cpp">#include <iostream> using namespace std;

int main() {

  int count = 7;   
  float avgWeight = 155.5F;   
 
  double totalWeight = count * avgWeight;   
  cout << "totalWeight=" << totalWeight << endl;   
  return 0;   

}</source>