Creating a thread of execution

On modern multi-core compilers, to achieve maximal performance (or just to provide a good user experience), programs usually use multiple threads of execution. Here is a motivating example in which we need to create and fill a big file in a thread that draws the user interface:

#include <cstddef> // for std::size_t

bool is_first_run(); 
 
// Function that executes for a long time.
void fill_file(char fill_char, std::size_t size, const char* filename);

// Called in thread that draws a user interface:
void example_without_threads() {
    if (is_first_run()) {
        // This will be executing for a long time during which
        // users interface freezes...
        fill_file(0, 8 * 1024 * 1024, "save_file.txt");
    }
}

Getting ready

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