#include<stdio.h>
#include<iostream.h>
void main()
{ int c=0;
FILE *fp;
if((fp=fopen("c:\\count.txt","wt+"))==NULL)
{
cout<<"can not open file"<<endl;
getchar();
}
c=fgetc(fp);
c++;
fputc(c,fp);
cout<<c<<endl;
fclose(fp);
}
能通过编译，但是文件不能写入，　达人帮忙啊！

那位能帮帮忙啊,

楼主什么意思啊？是想从一个文件中读出字符再写入原文件吗？本来那个文件就是空的，您什么也没读出来，当然什么也不会写入了。而且要有一个循环语句才能不停的读和写啊。
#include<stdio.h>
#include<iostream.h>
void main()
{ int c=0;char cc;
FILE *fp;
if((fp=fopen("c:\\count.txt","wt+"))==NULL)
{
cout<<"can not open file"<<endl;
getchar();
}
c=fgetc(fp);
c++;
while ((cc=getchar())!='\n')
fputc(cc,fp);
cout<<c<<endl;
fclose(fp);
}

int main()
{
const int MAXLEN=100;
const char filename[]="f:\\count.txt";

int count=0;
char buf[MAXLEN]={'0','\0'};

FILE *fp=0;
if(fp=fopen(filename,"r"))
{
char c;
while((c=fgetc(fp))!=EOF)
count=count*10+c-'0';
++count;
itoa(count,buf,10);
fclose(fp);
}
if(fp=fopen(filename,"w"))
{
char *p=buf;
while(*p!='\0')
fputc(*p++,fp);
fclose(fp);
}
else
{
cout<<"Can't not open file!"<<endl;
}
return 0;
}