<iomanip>

<iomanip> provides stream manipulators for formatting output: std::setw, std::setprecision, std::setfill, std::hex, std::oct, std::fixed, std::scientific. They temporarily modify the stream state for a single output operation.

Most modern code prefers std::format, but iomanip remains useful for legacy streams.

This example applies various formatting manipulators to control decimal precision, hexadecimal output, and field width.

// compile: g++ -std=c++11 -o iomanipexample iomanipexample.cpp
// run: ./iomanipexample
// description: stream formatting with manipulators
 
#include <iomanip>
#include <iostream>
 
int main() {
    double pi = 3.14159;
    int value = 255;
 
    std::cout << std::fixed << std::setprecision(2) << pi << "\n";
    std::cout << std::hex << value << "\n";
    std::cout << std::setw(10) << std::setfill('*') << 42 << "\n";
 
    return 0;
}