C++ std cout format example

demo_cout.cpp

#include <iostream>
#include <iomanip>

using namespace std;

void restore_fmt(std::_Ios_Fmtflags fmt)
{
	cout << "restore flag" << endl;
	cout.flags(fmt);
	cout << endl;
}

int main(int argc, char **argv)
{
	// backup the default FMT_FLAG
	std::_Ios_Fmtflags fmt_flag_orig = cout.flags();
	
	double i = 200.123456789;
	
	cout << "init val=" << i << endl;
	cout << endl;
	
	cout << "set width" << endl;
	cout << "|" << 12 << "|" << setw(6) << 12 << "|" << 12 << endl;
	cout << endl;
	
	cout << "set precision" << endl;
	cout << "|" << i << "|" << setprecision(3) << i << "|" << i << "|" << endl;
	cout << endl;
	
	restore_fmt(fmt_flag_orig);
	
	double i1 = 1234567.89;
	double i2 = 123.987654321;
	
	cout << "before set fixed" << endl;
	cout << "|" << i1 << "|" << i2 << "|" << endl;
	cout << endl;
	
	cout << "set fixed(sticky)" << endl;
	cout << fixed << "|" << i1 << "|" << i2 << "|" << endl;
	cout << endl;
	
	restore_fmt(fmt_flag_orig);
	
	cout << "set scientific(sticky)" << endl;
	cout << scientific << "|" << i1 << "|" << i2 << "|" << endl;
	cout << endl;
	
	restore_fmt(fmt_flag_orig);
	
	cout << "hex|dec|oct (sticky)" << endl;
	cout << "|dec: " << dec << "|" << 1024 << "|" << -1024 << "|" << endl;
	cout << "|hex: " << hex << "|" << 1024 << "|" << -1024 << "|" << endl;
	cout << "|oct: " << oct << "|" << 1024 << "|" << -1024 << "|" << endl;
	cout << endl;
	
	restore_fmt(fmt_flag_orig);
	
	cout << "boolean" << endl;
	cout << boolalpha << "|" << false << "|" << true << "|" << endl;
	cout << noboolalpha << "|" << false << "|" << true << "|" << endl;
	cout << endl;
	
	restore_fmt(fmt_flag_orig);
	
	return 0;
}

output:

init val=200.123

set width
|12|    12|12

set precision
|200.123|200|200|

restore flag

before set fixed
|1.23e+06|124|

set fixed(sticky)
|1234567.890|123.988|

restore flag

set scientific(sticky)
|1.235e+06|1.240e+02|

restore flag

hex|dec|oct (sticky)
|dec: |1024|-1024|
|hex: |400|fffffc00|
|oct: |2000|37777776000|

restore flag

boolean
|false|true|
|0|1|

restore flag