# <locale.h>

**[<locale.h>](https://en.cppreference.com/w/c/header/locale)** controls culture-specific formatting: decimal separators, currency symbols, sorting order. By default programs run in the `"C"` locale (ASCII, `.` decimal); call `setlocale(LC_ALL, "")` to use the user's environment locale.

Be careful with `LC_NUMERIC`—changing the decimal separator can break parsing of machine-generated data.

## Example

This example demonstrates how locale affects number formatting.

```c
// compile: gcc -o localeexample localeexample.c
// run: ./localeexample
// description: show how locale affects formatting

#include <locale.h>
#include <stdio.h>

int main() {
    double pi = 3.141592;
    
    setlocale(LC_ALL, "C");
    printf("C locale: %f\n", pi);
    
    setlocale(LC_NUMERIC, "de_DE.UTF-8");
    printf("German locale: %f\n", pi);
    
    return 0;
}
```