语法分析C程序

#include <stdio.h>
#include <string.h>
#include <ctype.h>
#define  MAXLEN 100
FILE *out;
char token[20],s[20];
char filename[25],outfile[25];
char ch;
FILE *fp = NULL;
char buff[MAXLEN];
int  bufflen = 0;
int  buffpos = -1;             

char blank[32][10]={"main","int","double","char","if","then","do",
"else","float","for","switch","continue","void","break","while"};       

int readchar(char * filename)  
  {
    if (fp == NULL)
      {
        if ((fp = fopen(filename,"r")) == NULL)
          {
            printf("File open error!\n");
            return 0;
          }
      }
   if (buffpos == -1)    
      {
        if (feof(fp))     
          {

            fclose(fp);    
            return -1;
          } 
       bufflen=fread(buff,sizeof(char),MAXLEN,fp);
       buffpos = 0;
     }
   if (buffpos < bufflen)
      ch = buff[buffpos++];        
   if (buffpos >= bufflen)
    buffpos = -1;
   return ch;
 }

void getbc( )
 {
   while(isspace(ch))        
   ch=readchar(filename);  
 }

void concatenate(char ch)
{
  strcat(token,&ch);      
}

void error( )             
 {
   if(ch!=-1)
   fputs("\n DATA ERROR!",out);
 }