How to stop large float numbers from exponentially output. (scientific notation?)

Question

I have a program that calculates population growth. It seems to work, but after the population exceeds 1 million, it is displayed as a decimal number increased to ten. (This is called scientific notation? exponential form? I forget.)

In any case, to output the data as a complete number? Here is the code to output where I will have to convert it.

#include "header.h" void output (float currentPopulation, float years, float birthRate, float deathRate) { cout << "the populaion in " << years << " years will be: " << estimatedPopulation (currentPopulation, years, birthRate, deathRate) << endl; } 

New code:

 #include "header.h" void output (float currentPopulation, float years, float birthRate, float deathRate) { cout << "the populaion in " << years << " years will be: " << fixed << setprecision(0) << estimatedPopulation (currentPopulation, years, birthRate, deathRate) << endl; } 

Answer 1

std::fixed manipulator used in conjunction with std::setprecision should help you (remember #include <iomanip> ).

Answer 2

With float, you get only 24 bits of accuracy, which is about 16,777,216. If you are dealing with numbers that exceed this and you need higher precision, consider using double , although I think you still have to do some formatting, to make it look the way you want. In this case, I recommend that you look at http://www.arachnoid.com/cpptutor/student3.html and http://www.fredosaurus.com/notes-cpp/io/omanipulators.html .

 cout << fixed << estimatedPopulation (currentPopulation, years, birthRate, deathRate) 

Answer 3

I suggest reading about std::scientific : http://msdn.microsoft.com/en-us/library/szb722da(VS.71).aspx

Answer 4

 float v(1234567891000000.0f); cout.precision(0); cout << fixed << v << endl; 

Note the loss of precision inherent in float: output is

1234567948140544

Answer 5

Use printf instead, for example printf("%f", myvalue) .