fio2.cpp

#include <iostream>
#include <cstdio>
#include <fstream>
#include <vector>
#include <conio.h>
int main()
{
    // prepare file
    std::ofstream("d:/test.txt") << 1 << ' ' << 2 << '\n';
    std::FILE* f;
    fopen_s(&f, "d:/test.txt", "r");

    std::vector<char> buf(4); // char is trivally copyable
    std::fread(&buf[0], sizeof buf[0], buf.size(), f);

    for (char n : buf)
        std::cout << n;

    std::vector<std::string> buf2; // string is not trivially copyable
    // this would result in undefined behavior
    //    std::fread(&buf2[0], sizeof buf2[0], buf2.size(), f);
    _getch();

    return 0;
}