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copied!<p>This is because <code>sizeof(char) == 1</code> and <code>sizeof(int) == 4</code>. The <code>std::ostream::write(const char*, size_t)</code> function interpret its last argument as the number of bytes to write. So when you write, you only write 2 bytes. The <code>std::istream::read(char*, size_t)</code> function also interpret its last argument as a number of bytes to read.</p> <p>So, using some diagram to represent you code, we have:</p> <pre><code>fstream F ( soubor1, ios::out | ios::binary ); unsigned int x = 0xc4; // x = // ,---------------------------. // | 0xc4 | 0x00 | 0x00 | 0x00 | // `---------------------------' F.write((const char*)&x, 1); // This write the first byte of x into the file, // that is it write the byte 0xc4 x = 0x8d; // x = // ,---------------------------. // | 0x8d | 0x00 | 0x00 | 0x00 | // `---------------------------' F.write((const char*)&x, 1); // This write the first byte of x into the file, // that is it write the byte 0x8d F.close(); F.open( soubor1, ios::in | ios::binary ); unsigned int a[2]; // a = // ,-------------------------------------------------------. // | ?? | ?? | ?? | ?? | ?? | ?? | ?? | ?? | // `-------------------------------------------------------' F.read((char*)&a[0], 2); // a = // ,-------------------------------------------------------. // | 0xc4 | 0x8d | ?? | ?? | ?? | ?? | ?? | ?? | // `-------------------------------------------------------' // You just read two bytes, while a point to a region that is // 8 bytes long. So only the first two bytes of the first int // are initialized, all the other value are undefined. </code></pre> <p>You can correct your code this way:</p> <pre><code>int main () { fstream F ( soubor1, ios::out | ios::binary ); unsigned int x = 0xc4; F.write ( ( char * ) &x, sizeof(unsigned int) ); x = 0x8d; F.write ( ( char * ) &x, sizeof(unsigned int) ); F.close(); F.open ( soubor1, ios::in | ios::binary ); unsigned a[2]; F.read((char*)a, 2 * sizeof(unsigned int)); for (size_t i = 0; i < 2; ++ i) cout << a[i] << " "; return 0; } </code></pre>

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