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  1. #include <iostream>
  2. using namespace std;
  3.  
  4.  
  5. int main()
  6. {
  7.     const double DIVISIOR = 2.0; //this represents how we come to our first "guess" basically the lazy (and wrong) way of finding a square root, taking the num
  8.     							//and dividing it by 2
  9.     double num = 0.0; //number we want the square root of
  10.     double guess = 0.0; //stores changing guesses as program runs
  11.     double root = 0.0; //stores changing roots as program runs
  12.     double finalAnswer = 0.0; //stores final answer to be displayed
  13.     double numOfApprox = 1.0; //loop control variable so our loop doesn't continue forever
  14.  
  15.  
  16.     //format numbers to display trailing decimal places
  17. 	cout.setf(ios::fixed); //I don't know what this is yet but the book says it will explain on chapter 8
  18. 	cout.setf(ios::showpoint); //this simply shows our decimal point
  19. 	cout.precision(3); //this is used to display a select number of places after the decimal
  20.  
  21.     //prompt user for input
  22.     cout << "Enter the number you want to find the square root of: \n"; //we first ask the user to enter the number they want the square root of
  23.     cout << "\n"; //this is here so everything isn't bunched together and the screen is more readable for the user
  24.     cin >> num; //the number the user wants the square root of is stored here and we'll be using this later
  25.     cout << "\n"; //this is here so everything isn't bunched together and the screen is more readable for the user
  26.  
  27.     //setup initial guess as a starting point
  28.     guess = num / DIVISIOR; //we take the users number and divide it by DIVISOR which has a value of 2. This is good enough for an initial guess
  29.  
  30.     //start looking for sq root
  31.     while((guess <= (guess + guess*1.01)) && (guess >= (guess - guess*1.01)) && (numOfApprox <=10.0)) //continue searching for a more approximate value until either A) the new guess is near 1 percent greater
  32.     																					//than the previous guess
  33.     																					//B) the guess is near 1 percent less than the previous guess
  34.     																					//C) we have guessed ten times, which is pretty approximate if you ask me
  35. 	{
  36.     	root = num / guess; //Now we take the number the user entered, divide it by our guess value 
  37.     						//the quotient value is the value of our root, which we will use to aid us in future approximations
  38.     	guess = (guess + root) / DIVISIOR; //Now we take our previous guess and add that to the value of root we just obtained in the line before
  39.     										//the sum of guess and root is divided by DIVISIOR and the quotient of this expression is the value of our new guess
  40.     	numOfApprox = numOfApprox + 1.0; //we increment numOfApprox so our loop doesn't run on forever if our guess isn't near one percent greater or less than the previous guess
  41.  
  42.  
  43. 	}
  44.  
  45. 	finalAnswer = guess; //giving our output variable the value obtained from the previous loop so we can output this later
  46.  
  47. 	cout.precision(5); //this is changed and now outputs 5 decimal places so we display the final result more accurately than the input
  48.  
  49. 	//output the inputs and outputs here
  50. 	if(finalAnswer <= 0.0)
  51. 	{
  52. 		cout << "The number " << num << " has no real square root."; //if the number is 0 or less then the number doesn't have a REAL root
  53. 		cout << "\n"; //this is here so everything isn't bunched together and the screen is more readable for the user
  54. 	} //if
  55. 	else
  56. 	{
  57. 		cout << "The square root of " << num << " is " << finalAnswer << "." << endl; //the number the user entered is displayed along with the approximate square root of that number
  58. 		cout << "\n"; //this is here so everything isn't bunched together and the screen is more readable for the user
  59. 	} //else
  60.  
  61.  
  62.  
  63.     system("pause");    // this keeps the console window from closing before we can see the output
  64.     return 0;           // return 0 to indicate successful execution of main()
  65. }
Compilation error #stdin compilation error #stdout 0s 0KB
comments (?)
stdin
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Standard input is empty
compilation info 
prog.cpp:63:5: error: use of undeclared identifier 'system'
    system("pause");    // this keeps the console window from closing before we can see the output
    ^
1 error generated.
stdout
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Standard output is empty
https://ideone.com/RJ9Y0Y
language:
C++14 (clang 8.0)
created:
10 years ago
visibility:
public

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