#include<iostream>#include<fstream>#include<cstdlib>using namespace std;class CntCharacters{private:  int cnt;public:  CntCharacters():cnt(0){}  ~CntCharacters(){}  void opentxt(char* p)  {    ifstream fin;    fin.open(p,ios_base::in);    if(!fin.is_open())    {     cout<<"cannot open the file,Please make sure the file is exist!/n";     exit(-1);    }    char temp;    while(!fin.eof())    {     fin>>temp;     if((temp>='a'&&temp<='z')||(temp>='A'&&temp<='Z'))cnt++;    }  }  void countthecharacter()  {   int count=0;   char nameoffile[80];   cout<<"Please enter the name of file:";   cin>>nameoffile;  //  scanf("%s",nameoffile);   opentxt(nameoffile);  }  void dis()  {   cout<<cnt<<endl;  }};int main(){  CntCharacters* c=new CntCharacters;  c->countthecharacter();  c->dis();  delete c;return 0;}

#include<iostream>#include<fstream>using namespace std;int main(){  fstream f("test.txt",ios::in);  char c;  int n=0;  while(f.get(c))n++;  cout<<n<<endl;  f.close();   return 0; }

#include<iostream>#include<fstream>using namespace std;int main(){  fstream f("test.txt",ios::in);  char c;  int n=0;  while(f>>c)n++;  cout<<n<<endl;  f.close();   return 0; }

//countch.cpp#include <iostream>#include <fstream>#include <string>using namespace std;int main(int argc, char* argv[]){  ifstream fin(argv[1]);  if (!fin) {    cout << "Can't open file - " << argv[1]       << "/nUseage : countch filename" << endl;    return 1;  }    string d;  int count = 0;  while ( getline(fin, d) ) //以行為單位讀入文件    count += d.size(); //累計字符數(shù)    cout << "/n Number of characters : "<< count << endl;}