#include "nsString.h" int main() { nsString str = "Hello, world!"; bool is_empty = str.IsEmpty(); if (is_empty) { printf("The string is empty.\n"); } else { printf("The string is not empty.\n"); } return 0; }This code initializes a string variable with the value "Hello, world!" and then uses the IsEmpty function to check whether it is an empty string or not. If it is empty, the program will output "The string is empty." Otherwise, it will output "The string is not empty." The nsString library is part of the Mozilla platform, and is included in packages such as Firefox and Thunderbird.