"Implementation of Lexical Analyzer"

#include
#include
#include
#include
FILE *fp;
char delim[14]={' ','\t','\n',',',';','(',')','{','}','[',']','#','<','>'};
char oper[7]={'+','-','*','/','%','=','!'};
char key[21][12]={"int","float","char","double","bool","void","extern","unsigned","goto","static","class","struct","for","if","else","return","register","long","while","do"};
char predirect[2][12]={"include","define"};
char header[6][15]={"stdio.h","conio.h","malloc.h","process.h","string.h","ctype.h"};
void skipcomment();
void analyze();
void check(char []);
int isdelim(char);
int isop(char);
int fop=0,numflag=0,f=0;
char c,ch,sop;
void main()
{
char fname[12];
clrscr();
printf("\n enter filename:");
scanf("%s",fname);
fp=fopen(fname,"r");
if(fp==NULL)
printf("\n the file does not exist");
else
analyze();
printf("\n end of file \n");
getch();
}
void analyze()
{
char token[50];
int j=0;
while(!feof(fp))
{
c=getc(fp);
if(c=='/')
{
//skip comment();
}
else if(c==’ ‘)
while((c=getc(fp))!="");
else if(isalpha(c))
{
if(numflag==1)
{
token[j]='\0';
check(token);
numflag=0;
j=0;
f=0;
}
else
{
token[j]=c;
j++;
}
if(f==0)
f=1;
}
else if(isalnum(c))
{
if(numflag==0)
numflag=1;
token[j]=c;
j++;
}
else
{
if(isdelim(c))
{
if(numflag==1)
{
token[j]='\0';
check(token);
numflag=0;
}
if(f==1)
{
token[j]='\0';
numflag=0;
check(token);
}
j=0;
f=0;
printf("\n delimiters \t%c",c);
}
else if(isop(c))
{
if(numflag==1)
{
token[j]='\0';
check(token);
numflag=0;
j=0;
f=0;
}
if(f==1)
{
token[j]='\0';
j=0;
f=0;
numflag=0;
check(token);
}
if(fop==1)
{
fop=0;
printf("\n operator \t %c%c",c,sop);
}
else
printf("\n operator \t%c",c);
}
else if(c=='.')
{
token[j]=c;
j++;
}
}
}
}
int isdelim(char c)
{
int i;
for(i=0;i<14;i++)
{
if(c==delim[i])
return 1;
}
return 0;
}
int isop(char c)
{
int i,j;
char ch;
for(i=0;i<7;i++)
{
if(c==oper[i])
{
ch=getc(fp);
for(j=0;j<6;j++)
{
if(ch==oper[j])
{
fop=1;
sop=ch;
return 1;
}
}
ungetc(ch,fp);
return 1;
}
}
return 0;
}
void check(char t[])
{
int i;
if(numflag==1)
{
printf("\n number \t\t%s",t);
return;
}
for(i=0;i<2;i++)
{
if(strcmp(t,predirect[i])==0)
{
printf("\n preprocessor directive %s",t);
return;
}
}
for(i=0;i<6;i++)
{
if(strcmp(t,header[i])==0)
{
printf("\n header file \t%s",t);
return;
}
}
for(i=0;i<21;i++)
{
if(strcmp(key[i],t)==0)
{
printf("\n keyword \t\t%s",key[i]);
return;
}
}
printf("\n identifier \t%s",t);
}
void skipcomment()
{
ch=getc(fp);
if(ch=='/')
{
while((ch=getc(fp))!='\0');
}
else if(ch=='*')
{
while(f==0)
{
ch=getc(fp);
if(c=='/')
f=1;
}
}
f=0;
}