程序代码：

 string::iterator iter = str.begin();
    while (iter != str.end()) {
        ch = *iter++;
        for (int i = 0; i < 8; ++i)
            cout << ((ch >> i) & 1);
    }

程序代码：

#include <string>
#include <iostream>
using namespace std;

int main()

 {
    string str;
    FILE *fp;
    char ch;
    if((fp=fopen("file.txt","wb+"))==NULL)
    {
        cout<<"can not open this file.\n";
        return 0;
    }
    cin >> str;
    string::iterator iter = str.begin();
    while (iter != str.end()) {
        ch = *iter++;
        for (int i = 0; i < 8; ++i)
                fputc(((ch >> i) & 1),fp);
    }
    fclose(fp);
}