Set/Unset uppercase format flag
  uppercase sets the format flag to use uppercase letters instead of lowercase for representations on insert operations involving stream-generated letters, like some hexadecimal representations and numeric base prefices.
  nouppercase unsets this flag, using lowercase letters on these insert operations.

Parameters.

str

Stream object where to apply. This is a manipulator parameter.

Return Value.
  A reference to the stream object.

Example.

// modify uppercase flag
#include <iostream>
using namespace std;

int main () {
  cout << showbase << hex;
  cout << uppercase << 77 << endl;
  cout << nouppercase << 77 << endl;
  return 0;
}

See also.
  flags, setf, unsetf
  ios_base class