Is it a bad input : cin « Development « C++ Tutorial






#include <iostream>
#include <string>
#include <cmath>

using namespace std;

int main()
{  
   double area;
   cout << "Please enter the area of a square: ";
   cin >> area;

   if (cin.fail())
   {
      cout << "Error: Bad input\n";
      return 1;
   }

   if (area < 0)
   {
      cout << "Error: Negative area.\n";
      return 1;
   }

   cout << "The side length is " << sqrt(area) << "\n";

   return 0;
}








5.1.cin
5.1.1.Read int value from keyboard
5.1.2.cin Handles Different Data Types
5.1.3.Use get() to read a string that contains spaces
5.1.4.Use the extraction operator >> with cin.get( ) to process an entire string.
5.1.5.cin with strings (cin.getline)
5.1.6.cin and atoi, atof functions
5.1.7.Using peek() and putback()
5.1.8.Concatenate put()
5.1.9.Testing error states.
5.1.10.Unformatted I/O using cin.read, cin.gcount and cout.write
5.1.11.Contrasting input of a string via cin and cin.get
5.1.12.Demonstrating member function width
5.1.13.Read char array from keyboard, get its length and concatenate two strings
5.1.14.Read a character from keyboard
5.1.15.Copy all standard input to standard output
5.1.16.Manipulator that skips until end-of-line
5.1.17.avoids buffer overflow with cin.width
5.1.18.Extends std::streambuf to create data buffer
5.1.19.Using member functions get, put and eof.
5.1.20.Contrasting input of a string with cin and cin.get.
5.1.21.Unformatted I/O with read, gcount and write.
5.1.22.Character input with member function getline.
5.1.23.Is it a bad input