fwrite & fread use

Every file operation mode switch must call fclose to close the file.

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If the direct switching operation mode , file corruption (garbled) or operation fails.

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When calling the fclose, be recovered as a file pointer parameters must be defined again, it is preferable functional package.

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When the memory array, fwrite size_t size parameter can be used sizeof (buffer [0]), size_t count may be used sizeof (buffer) / sizeof (buffer [0]).

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fread returns an integer, which is the number of successfully read the data, which is the maximum value of the parameter size_t count.

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When using sequential read cycle while (! Feof (stream)), fread trigger-file condition after an incomplete reading.

one example:

#include<iostream>
#include<fstream>

int main()
{
    using std::cin;
    using std::cout;
    using std::endl;
    cout << "Hello, I am a C++ test program." << endl; 
    cin.get();
    //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
    
    FILE* _f0;
    _f0 = fopen("f0.txt", "wb");
    if (_f0 != NULL) 
    {
        cout << "I created a file named \"f0\"." << endl;
        cin.get();
        int buf[8];
        cout << "size of buf[0] = " << sizeof(buf[0]) << endl
            << "size of buf = " << sizeof(buf) << endl;

        for (int i = 0; i < 8; i++)
        {
            buf[i] = '0' + i;
        }
        fwrite(buf, sizeof(buf[0]), sizeof(buf)/sizeof(buf[0]), _f0);
        cout << "Then put some numbers into this file." << endl;
        cin.get();
        cout << "Read out these numbers:" << endl;
        fclose(_f0);
        FILE* _f1 = fopen("f0.txt", "rb");
        cout << "f0 = " << _f1 << endl;
        int i = 0;
        int R = 0;
        int n = 0;
        while (!feof(_f1))
        {
            n = fread(&R, sizeof(R), 1, _f1);
            cout << "n = " << n << " buf[" << i << "] = " << R << endl;
            i++;
        }
        fclose(_f1);
        cout << "At last, add a number to the file." << endl;
        FILE* _f2 = fopen("f0.txt", "ab");
        R = '8';
        fwrite(&R, sizeof(R), 1, _f2);
        fclose(_f2);
    }
    else 
    {
        cout << "File creating failed." << endl;
    }
    
    //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
    cout << endl << "Press enter to end.";
    cin.get();
    return 0;
}