1 #include<stdio.h>
  2 #include<windows.h>
  3 #define INPUTFILE  "input.c"
  4 #define OUTPUTFILE "output.c"     
  5 
  6 enum Status{
  7     NULLSTATUS,
  8     CPPSTATUS,
  9     CSTATUS,
 10     EOFSTATUS,
 11 }; 
 12 int  status = NULLSTATUS;
 13 
 14 void do_null_status(FILE *ifp,FILE *ofp){  //  初始态为普通状态 (没有参与注释部分的内容 )
 15     int c1=fgetc(ifp);
 16     switch(c1){           
 17         case '/':{  
 18             int c2 = getc(ifp);
 19             switch(c2){           //   .../*  
 20                 case '*':
 21                     fputc('/',ofp);
 22                     fputc('/',ofp);
 23                     status = CSTATUS;
 24                     break;
 25                 case '/':         //     ... // 
 26                     fputc('/',ofp);
 27                     fputc('/',ofp);
 28                     status = CPPSTATUS;
 29                     break;
 30                 case EOF:
 31                     fputc('/',ofp);
 32                     status = EOFSTATUS;
 33                     break;
 34                 default:         //     .../ ...
 35                     fputc('/',ofp);
 36                     fputc(c2,ofp);
 37                     break;
 38             }
 39             break;
 40         }
 41         case EOF:
 42             status = EOFSTATUS;
 43             break;
 44         default:
 45             fputc(c1,ofp);
 46             break;
 47     }
 48 }
 49 void do_cpp_status(FILE *ifp,FILE *ofp){     // 已进入C++风格注释（// ...)  保持此种风格注释 
 50     int c = fgetc(ifp);  
 51     switch (c) {
 52         case '\n' :            //   ....\n
 53             fputc('\n',ofp);
 54             status = NULLSTATUS;
 55            break;
 56         case EOF :
 57             status = EOFSTATUS;
 58            break;
 59         default:
 60            fputc(c, ofp);
 61           break;
 62     }
 63 }
 64 void do_c_status(FILE *ifp,FILE *ofp){    //  进入C风格注释 ( /* ...)  目的改为C++风格注释 
 65     int c1= fgetc(ifp);
 66     switch(c1)
 67     {
 68         case '*':{
 69             int c2= fgetc(ifp);
 70             switch(c2){
 71                 case '/' :             //   //...*/...          
 72                     fputc('\n' ,ofp);                           
 73                     status = NULLSTATUS;
 74                      break;
 75                  case EOF:
 76                      fputc('*' ,ofp);
 77                      status = EOFSTATUS;
 78                 default:
 79                     fputc('*',ofp);
 80                     ungetc(c2, ifp);      //这个地方调了好多遍才注意到，实在是愚钝。 
 81                     break;
 82             }
 83             break;
 84         }    
 85         case '\n':     //      /*  ... \n
 86             fputc('\n', ofp);
 87             fputc('/' , ofp);
 88             fputc('/' , ofp);
 89             break;
 90         case EOF:
 91             status= EOFSTATUS;
 92             break;
 93         default:       //   /* ... 
 94             fputc(c1,ofp);
 95             break;        
 96     }
 97 }
 98 void convert_work(FILE *ifp,FILE *ofp){
 99     while( status != EOFSTATUS){
100         switch(status){
101             case NULLSTATUS :
102                 do_null_status(ifp,ofp);
103                 break;
104             case CPPSTATUS :
105                 do_cpp_status(ifp,ofp);
106                 break;    
107             case CSTATUS :
108                 do_c_status(ifp,ofp);
109                 break;
110             case EOFSTATUS:
111                 break;
112             default:
113                 break;
114         }
115     }
116 }
117 int main(){
118     FILE *ifp=fopen(INPUTFILE,"r");
119     FILE *ofp=fopen(OUTPUTFILE,"w");
120     if(ifp == NULL || ofp == NULL){
121         perror(" Open failed\n");
122         exit(1);
123     }
124     convert_work(ifp , ofp);
125     fclose(ifp);
126     fclose(ofp);
127     system("pause");
128     return  0;
129 } 

实例测试：