C++<iomanip> control character

C++<iomanip> Control C + + cout output format

The following header files are often seen in C + + programs
#include <iomanip>
IO represents the input and output, MANIP is the abbreviation of the manipulator (manipulator)
The role of Iomanip:
Mainly for cin,cout, such as some manipulation operators, such as setfill,setw,setbase,setprecision and so on. It is the I/O flow control header file, just like the formatted output in C. Here are some common control functions:
Dec base is 10 equivalent to "%d"
Hex base is 16 equivalent to "%x"
The OCT has a base of 8 equivalent to "%o"
Setfill (' C ') set the fill character to C
Setprecision (n) Set display decimal precision is n bit
SETW (n) Set a field width of n characters
This control means that the output width is guaranteed to be N. Such as:
cout << SETW (3) << 1 << setw (3) << << SETW (3) << + << Endl; The output result is
1 10100 (the default is right-aligned) when the output length is greater than 3 o'clock (<<1000), SETW (3) does not work.
▲SETW (N) Usage: Popularly speaking is preset width
such as cout<<SETW (5)<<255<<endl;
The result is:
Spaces (space) 255
▲setfill (char c) Usage: that is, if there is already a unused width size in the preset width, fill with the character C that is set
such as Cout<<setfill (' @ ') &LT;&LT;SETW (5) <<255<<endl;
The result is:
@@255
▲setbase (int n): Converts a number to n binary.
such as Cout<<setbase (8) &LT;&LT;SETW (5) <<255<<endl;
Cout<<setbase (&LT;&LT;SETW) (5) <<255<<endl;
Cout<<setbase (<<255<<endl;)
The result is:
(space) (space) 377
Spaces (space) 255
Spaces (space) F F
▲setprecision usage
Use Setprecision (n) to control the number of floating-point numbers displayed by the output stream. The default stream output value for C + + is 6.
If Setprecision (n) is combined with setiosflags (ios::fixed), you can control the number of digits to the right of the decimal point. Setiosflags (ios::fixed) is a fixed-point representation of real numbers.
If combined with setiosnags (ios::scientific), you can control the number of decimal digits of exponential notation. Setiosflags (ios::scientific) is an exponential representation of real numbers.
Setiosflags (ios::fixed) fixed floating-point display
Setiosflags (ios::scientific) index indicates
Setiosflags (ios::left) Align Left
Setiosflags (ios::right) Align Right
Setiosflags (IOS::SKIPWS) ignores leading whitespace
Setiosflags (ios::uppercase) 16 Decimal Capital Output
Setiosflags (ios::lowercase) 16 binary lowercase output
Setiosflags (ios::showpoint) force display decimal point
Setiosflags (ios::showpos) force display symbols
Example:
#include <iostream.h>
#include <iomanip.h>
using namespace Std;
int main ()
{
cout<<12345.0<<endl;//Output "12345"
Cout<<setiosflags (ios::fixed) <<setprecision (3) <<1.2345<<endl; output "1.235"
Cout<<setiosflags (ios::scientific) <<12345.0<<endl;//output "1.234500e+004"
Cout<<setprecision (3) <<12345.0<<endl;//output "1.235e+004" (1.235e+004 should be changed to 1.23e+004)
return 0;
}

C++<iomanip> control character

C++<iomanip> control character