shiyan.c

运行环境：win—tc。 能实现一下功能： 1）从键盘读入数据

#include<stdio.h>
#include<string.h>
#include<ctype.h>
#include<math.h>
#define MAXSIZE 100
#define N 50
void init(char *ch)
{ char newc[N];
  newc[0]=NULL;
  strcpy(ch,newc);}
void scan(char *ch)
{ char *k1="if";
  char *k2="then";
  char *k3="else";    
  char *k4="while";
  char *k5="do";
  char *k6="+";
  char *k7="-";
  char *k8="*";
  char *k9="/";
  char *k10=">";
  char *k11="<";
  char *k12="=";
  char *k13="(";
  char *k14=")";
  int judge;    
  int i=1,k;
  int answer=0;
  if(strcmp(ch,k1)==0||strcmp(ch,k2)==0||strcmp(ch,k3)==0||strcmp(ch,k4)==0||strcmp(ch,k5)==0)
     printf("keywords\t%s\n",ch);
  else  if (isalpha(ch[0])!=0)
             printf("IDN\t%s\n",ch);

  { if(strcmp(ch,k6)==0||strcmp(ch,k7)==0||strcmp(ch,k8)==0||strcmp(ch,k9)==0||strcmp(ch,k10)==0||
    strcmp(ch,k11)==0||strcmp(ch,k12)==0||strcmp(ch,k13)==0||strcmp(ch,k14)==0)
    {printf("operator\t%s\n",ch);}
   else
{ if(isdigit(ch[0])==2)
 {if(strlen(ch)>1)
  {if(strlen(ch)>2)
   {if(ch[1]=='x')
         {i=2;judge=1;
  while(ch[i]!=NULL)
  {if(isxdigit(ch[i])==0)
   { judge=0;}
    i++; }
   if(judge==1)
   {for(i=2;i<strlen(ch);i++)
    {if(ch[i]>='0'&&ch[i]<='9')
     {k=ch[i]-'0';}
     else
     {k=ch[i]-'W';}
     answer=answer+k*pow(16,strlen(ch)-i-1);}
     printf("INT16\t%s\t%d\n",ch,answer);}

  else printf("Input error %s is not a hexadecimal number!\n",ch) ;
        }
      }

      if(ch[0]=='0')
      {i=1;judge=1;
      while(ch[i]!=NULL)
     {if(isdigit(ch[i])==0)
         {judge=0;}
          i++;}
      if(judge==1)                      
      {
      for(i=0;i<strlen(ch);i++)
       {if(ch[i]>='8'){judge=3;break;}

       k=ch[i]-'0';answer=answer+k*pow(8,strlen(ch)-i-1);}
       if(judge==3)printf("Input  error %s is not a octal number !\n",ch);
       else printf("INT8\t%s\t%d\n",ch,answer);}}
      else
      {i=1;judge=1;
       while(ch[i]!=NULL)
      {if(isxdigit(ch[i])==0)
       {judge=0;}
        i++;}
     if(judge==1)
     {printf("INT10\t%s\n",ch);}}}
  if(strlen(ch)==1)
     {printf("INT10\t%s\n",ch);}}

  /*else{printf("IDN\t%s\n",ch);}}}}  */
 }} }
   main()
{ char token[MAXSIZE];
  char pretoken[MAXSIZE];
  char aftoken[N];
 /* 用来存放分割后的各个字符串 */   
 char ch[2];           
 /* 预处理过程和分割字符串的过程中起到存放字符的作用,然后再用字符连接函数strcat添加新字符到字符串中 */   
 int i=0,j=0;  
  ch[1]='\0';  
  printf("Please input:");    
gets(token);   
 while(token[i]==' ')   
 { i++;}
 while(token[i]!=NULL)   
 { token[j]=token[i];
   i++;
   j++;    }
   token[j]=NULL;
   i=0;
 while(token[i]!=NULL)    
{  ch[0]=token[i];
  if(ch[0]==' ')
{strcat(pretoken,ch);
j=1;
 while(token[i+j]==' ')
 {j++;}
 i=i+j-1;}
 else{strcat(pretoken,ch);}
 i++; }
     /* 以上三个while,用于预处理,去掉多余的空格 */   
 i=0;    
while(pretoken[i]!=NULL)
{ ch[0]=pretoken[i];
if(ch[0]=='+'||ch[0]=='-'||ch[0]=='*'||ch[0]=='/'||ch[0]=='>'||ch[0]=='<'||ch[0]=='='||ch[0]=='('||ch[0]==')')
{ if(strlen(aftoken)!=0)
{ scan(aftoken);
  init(aftoken);
  strcat(aftoken,ch);
  scan(aftoken);
  init(aftoken);}
  else
  {strcat(aftoken,ch);
   scan(aftoken);
   init(aftoken);}
   i++;
   continue;}
   if(ch[0]==' ')
   {if(strlen(aftoken)!=0)
   {scan(aftoken);
    /*init(aftoken);  */
    }}
    else
    {strcat(aftoken,ch);}
    i++;}
/*把单个单词分出来,转入专门的识别处理程序*/    
if(strlen(aftoken)!=0)   
 {scan(aftoken);}
 getch();}