#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <assert.h>

int main(int argc, char* argv[]) {
    char const* filename = __FILE__ ".bin"; // "write_double.c.bin"
    // file opened in wrtie mode
    // no indicator here its a binary file
    FILE* file = fopen(filename, "w");

    // writing
    double num = 1234.0;
    fwrite(&num, sizeof(num), 1, file);

    // don't forget to close
    fclose(file);

    return EXIT_SUCCESS;
}
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