#include "stdafx.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <malloc.h>
#include <ctype.h>
#include <conio.h>
#define NULL 0
FILE *fp;
char ch;
char *keyword[8]={"do","begin","else","end","if","then","var","while"};
char *operatornum[4]={"+","-","*","/"};
char *comparison[6]={"<","<=","=",">",">=","<>"};
char *interpunction[6]={",",";",":=",".","(",")"};
//////////////////////////////////////////////////////////////////////////////////////////
bool search(char searchstr[],int wordtype)
{
 int i;
 switch (wordtype)
 {
 case 1:for(i=0;i<=7;i++)
     {
      if(strcmp(keyword[i],searchstr)==0)
       return(true);
      
     }
 case 2:{
  for(i=0;i<=3;i++)
  {
   if(strcmp(operatornum[i],searchstr)==0)
    return(true);
  }
  break;
     }
 case 3: for(i=0;i<=5;i++)
   {
    if(strcmp(comparison[i],searchstr)==0)
     return(true);
   }
 case 4: for(i=0;i<=5;i++)
   {
    if(strcmp(interpunction[i],searchstr)==0)
     return(true);
   }
  
 
 }
 return(false);
}


///////////////////////////////////////////////////////////////////////////////////////////

char letterprocess (char ch)//字母處理函數
{
 int i=-1;
 char letter[20];
 while (isalnum(ch)!=0)
 {
  letter[++i]=ch;
  ch=fgetc(fp);
 };
 letter[i+1]='\0';
 if (search(letter,1))
 {
  printf("<%s,->\n",letter);
  //strcat(letter,"\n");
  //fputs('<' letter '>\n',outp);
 }
 else
 {
  printf("<indentifier,%s>\n",letter);
  //strcat(letter,"\n");
  //fputs(letter,outp);
 }
 return(ch);
}
///////////////////////////////////////////////////////////////////////////////////////////

char numberprocess(char ch)//數字處理程序
{
 int i=-1;
 char num[20];
 while (isdigit(ch)!=0)
 {
  num[++i]=ch;
  ch=fgetc(fp);
 }
 if(isalpha(ch)!=0)
 {
  while(isspace(ch)==0)
  {
   num[++i]=ch;
            ch=fgetc(fp);
  }
  num[i+1]='\0';
  printf("錯誤！非法標識符：%s\n",num);
  goto u;
 }
 num[i+1]='\0';
    printf("<num,%s>\n",num);
    //strcat(num,"\n");
    //fputs(num,outp);
u: return(ch);
}

//////////////////////////////////////////////////////////////////////////////////////////////

char otherprocess(char ch)
{
 int i=-1;
 char other[20];
 if (isspace(ch)!=0)
 {
  ch=fgetc(fp);
  goto u;
 }
 while ((isspace(ch)==0)&&(isalnum(ch)==0))
 {
  other[++i]=ch;
  ch=fgetc(fp);
 }
 other[i+1]='\0';
 if (search(other,2))
  printf("<relop,%s>\n",other);
 else
  if (search(other,3))
   printf("<%s,->\n",other);
  else
   if (search(other,4))
    printf("<%s,->\n",other);
   else 
    printf("錯誤！非法字符：%s\n",other);
u: return (ch);
}


/////////////////////////////////////////////////////////////////////////////////////////////
void main ()
{
 char str,c;
 printf("**********************************詞法分析器************************************\n");
 //outp=fopen("二元式表.txt","w");
 if ((fp=fopen("目標程序.txt","r"))==NULL)
  printf("源程序無法打開！\n");
 else
 {
  str =fgetc(fp);
  while (str!=EOF)
  {
   if (isalpha(str)!=0)
    str=letterprocess(str);
   else
   {
    if (isdigit(str)!=0)
     str=numberprocess(str);
    else
     str=otherprocess(str);
   }
    
  };
  printf("詞法分析結束，謝謝使用！\n");
  printf("點任意鍵退出!\n");
 }
   c=getch();
}
目標程序：
ht1984=1000


程序運行結果：

 **********************************詞法分析器************************************

<indentifier,ht1984>
<=,->
<num,1000>
詞法分析結束，謝謝使用！
點任意鍵退出!