void read_back(const char *filename)
{
    FILE* pFile;
    long lSize=100;
    char* buffer;
    buffer = (char*)malloc(sizeof(char)*lSize);
    pFile = fopen(filename, "rb");
    if (pFile == NULL) { fputs("File error", stderr); exit(1); }

    // copy the file into the buffer:
    size_t result = fread(buffer, 1, lSize, pFile);
    if (result != lSize) { fputs("Reading error", stderr); exit(3); }
       fclose(pFile);
}

int main()
{
    const char *fname[2];
    fname[1] = "C:\1_data.bin";
    fname[2] = "C:\2_data.bin";
    fname[3] = "C:\3_data.bin";

    for (int i = 0; i < 2; ++i)
    {
        read_back(fname[i]);
    }
    return 0;
}

const char *fname[3];
    fname[0] = "C:\1_data.bin";
    fname[1] = "C:\2_data.bin";
    fname[2] = "C:\3_data.bin";

if (result != lSize) { fputs("Reading error", stderr); exit(3); }