Using hex, oct, dec and setbase stream manipulators.
#include <iostream> #include <iomanip> using std::cout; using std::cin; using std::endl; using std::hex; using std::dec; using std::oct; using std::setbase; int main() { int n; cout << "Enter a decimal number: "; cin >> n; cout << n << " in hexadecimal is: " << hex << n << '\n' << dec << n << " in octal is: " << oct << n << '\n' << setbase( 10 ) << n << " in decimal is: " << n << endl; return 0; }