#include
     
           //包含库所用的某些宏和变量#include
      
           //包含库#include
       
            //包含字符串处理库#define _KEY_WORD_END "waiting for your expanding"     //定义关键字结束标志typedef struct  {         int typenum;           char * word;}WORD;char input[255];      //输入换缓冲区char token[255]="";   //单词缓冲区int p_input;          //输入换缓冲区指针int p_token;          //单词缓冲区指针char ch;              //当前所读的字符char *rwtab[]={
   "begin","if","then","while","do","end",_KEY_WORD_END};        //C语言关键字WORD * scaner();    //词法扫描函数，获得关键字main(){           int over=1;           WORD *oneword;           oneword=(WORD *)malloc(sizeof(WORD));           printf("Enter Your words(end with #):");   //读入源程序字符串到缓冲区，以#结束，允许多行输入             scanf("%[^#]s",input);                                  p_input=0;           printf("Your words:%s\n\n",input);         while(over<1000&&over!=-1)          {                  oneword=scaner();                  printf("单词符号:%s\t种别码:%d\n",oneword->word,oneword->typenum);                  over=oneword->typenum;          }}char m_getch(){              ch=input[p_input];            p_input=p_input+1;            return (ch);}//去掉空白字符void getbc(){          while(ch==' '||ch==10)       {          ch=input[p_input];          p_input=p_input+1;          }}//拼接单词void concat(){          token[p_token]=ch;          p_token=p_token+1;        token[p_token]='\0';}//判断是否字母int letter(){           if(ch>='a'&&ch<='z'||ch>='A'&&ch<='Z')                 return 1;           else                 return 0;}//判断是否数字int digit(){           if(ch>='0'&&ch<='9')                    return 1;           else                    return 0;}//检索关键字表格int reserve(){        int i=0;          while(strcmp(rwtab[i],_KEY_WORD_END))          {                  if(!strcmp(rwtab[i],token))                 {                            return i+1;                }                 i=i+1;        }          return 10;}//回退一个字符void retract(){         p_input=p_input-1;}WORD *scaner(){           WORD *myword ;          myword=(WORD *)malloc(sizeof(WORD));         myword->typenum=10;         myword->word="";           p_token=0;           m_getch();           getbc();         if(letter()){               while(letter()||digit()){                      concat();                     m_getch();             }                retract();                   myword->typenum=reserve();                 myword->word=token;             return(myword);           }         else if(digit()){                while(digit())                     {                              concat();                             m_getch();                       }                        retract();                        myword->typenum=20;                         myword->word=token;                        return(myword);             }                else               {                        switch(ch)                        {                         case '+':                             myword->typenum=13;                                 myword->word="+";                              return(myword);                                                         break;                        case '-':                             myword->typenum=14;                            myword->word="-";                                   return(myword);                              break;                         case '*':                             myword->typenum=15;                               myword->word="*";                             return(myword);                            break;                      case '/':                              myword->typenum=16;                            myword->word="/";                             return(myword);                             break;                        case ':':  m_getch();                          if(ch=='='){                              myword->typenum=18;                                   myword->word=">=";                                   return(myword);                          }                          retract();                             myword->typenum=17;                              myword->word=":";                             return(myword);                            break;                      case '<':  m_getch();                          if(ch=='='){                              myword->typenum=21;                                   myword->word="<=";                                   return(myword);                                                      }                                                    else if(ch=='>'){                              myword->typenum=22;                                   myword->word="<>";                                   return(myword);                                                        }                          retract();                            myword->typenum=20;                             myword->word="<";                             return(myword);                            break;                                                     case '>':  m_getch();                          if(ch=='='){                              myword->typenum=24;                                   myword->word=">=";                                   return(myword);                          }                          retract();                                                        myword->typenum=23;                               myword->word=">";                               return(myword);                                break;                                                case '=':                             myword->typenum=25;                               myword->word="=";                             return(myword);                            break;                      case ';':                            myword->typenum=26;                             myword->word=";";                            return(myword);                              break;                                                    case '(':                             myword->typenum=27;                               myword->word="(";                             return(myword);                            break;                      case ')':                             myword->typenum=28;                               myword->word=")";                             return(myword);                            break;                                            case '#':                             myword->typenum=0;                            myword->word="OVER";                              return(myword);                             break;                      default:                                     myword->typenum=-1;                                        myword->word="ERROR";                                     return(myword);                                 }                  }  }