If you want FF rather than ff, you need to use std::uppercase, too
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#include <iostream>
#include <iomanip>
int main()
{
int x = 255;
std::cout << std::hex << x << std::dec << std::endl;
std::cout << std::hex << std::uppercase << x << std::nouppercase << std::dec << std::endl;
return 0;
}
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(Note I've added std::dec -- and std::nouppercase -- immediately after I'd finished outputting the numbers, so I know the formatting is going to be back to the default for future insertions. If I was writing a hex editor, I'd use std::hex, etc. once, as a distinct init step, to make hex the default.)
When I output hex numbers, I like to display the prefix. This involves a bit more work.
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#include <iostream>
#include <iomanip>
int main()
{
using namespace std;
int x = 2;
int y = 255;
cout << showbase // show the 0x prefix
<< internal // fill between the prefix and the number
<< setfill('0'); // fill with 0s
cout << hex << setw(4) << x << dec << " = " << setw(3) << x << endl;
cout << hex << setw(4) << y << dec << " = " << setw(3) << y << endl;
return 0;
}
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Unfortunately, uppercase causes the Ox prefix to become 0X, so if I want uppercase hex, I alter the code to output the 0x explicitly, and omit the showbase.
Andy
P.S. If you do a lot of formatting changes, it can be easier to cache the formatting flags, etc. and restore them afterwards (or an equivalent class, if you want to be tidier)
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void WriteLotsOfOutput()
{
using namespace std;
ios_base::fmtflags oldFlags = cout.flags();
streamsize oldPrec = cout.precision();
char oldFill = cout.fill();
// Do lots of output
cout.flags(oldFlags);
cout.precision(oldPrec);
cout.fill(oldFill);
}
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