Prevent scientific notation in ostream when using << with double

Question

I need to prevent my double to print in scientific notation in my file,

when I do this

outfile<<X;

Answer 1

you can use format flags

http://www.cplusplus.com/reference/iostream/ios_base/fmtflags/

Answer 2

Here's an example of usage http://cplus.about.com/od/learning1/ss/clessontwo_4.htm

as per your question use

cout<< fixed<< a<< endl;

Answer 3

To set formatting of floating variables you can use a combination of setprecision(n), showpoint and fixed. In order to use parameterized stream manipulators like setprecision(n) you will have to include the iomanip library:

#include <iomanip>

setprecision(n): will constrain the floating-output to n places, and once you set it, it is set until you explicitly unset it for the remainder of the stream output.

fixed: will enforce that all floating-point numbers are output the same way. So if your precision is set to 4 places, 6.2, and 6.20 will both be output as:

6.2000
6.2000

showpoint: will force the decimal portions of a floating-point variable to be displayed, even if it is not explicitly set. For instance, 4 will be output as:

4.0

Using them all together:

outfile << fixed << showpoint;
outfile << setprecision(4);
outfile << x;