3.Write a Program to develop a lexical analyzer to recognize a few patterns.

 

Input.c

#include<stdio.h>

#include<conio.h>

void main()

{

int a=10,b,c;

a=b*c;

getch();

}

Key.c

#include<stdio.h>

#include<conio.h>

void main()

{

int a=10,b,c;

a=b*c;

getch();

}

int

void

main

char

if

for

while

else

printf

scanf

FILE

include

stdio.h

conio.h

iostream.h

 

 

oper.c

 

( open para

) close para

{ open brace

} close brace

< lesser

> greater

" doublequote

'singlequote

: colan

; semicolan

# preprocessor

= equal

== asing

+ add

- sub

* mult

% percentage

/ slash

\ backslash

^ bitwise

& reference

 

 

Program.c

 

#include<stdio.h>

//#include<conio.h>

#include<ctype.h>

#include<string.h>

 

void main()

{

FILE *fi,*fo,*fop,*fk;

int flag=0,i=1;

char c,t;

char a[15],ch[15],file[20];

 

printf("\n enter the file name\n");

scanf("%s",&file);

fi=fopen(file,"r");

fo=fopen("inter.c","w");

fop=fopen("oper.c","r");

fk=fopen("key.c","r");

c=getc(fi);

 

while(!feof(fi))

{

  if(isalpha(c)||isdigit(c)||(c==']'||c=='['||c=='.'==1))

  fputc(c,fo);

  else

  {

   if(c=='\n')

     fprintf(fo,"\t$\t");

    else

     fprintf(fo,"\t%c\t",c);

  }

c=getc(fi);

}

fclose(fi);

fclose(fo);

fi=fopen("inter.c","r");

 

printf("\nlexical analysis\n");

fscanf(fi,"%s",a);

 

printf("\nline %d\n",i++);

while(!feof(fi))

{

if(strcmp(a,"$")==0)

{

printf("\nline %d\n",i++);

fscanf(fi,"%s",a);

}

 

while(!feof(fop))

{

if(strcmp(ch,a)==0)

{

fscanf(fop,"%s",ch);

printf("\t\t%s\t:\t%s\n",a,ch);

flag=1;

}

fscanf(fop,"%s",ch);

}

rewind(fop);

fscanf(fk,"%s",ch);

 

while(!feof(fk))

{

if(strcmp(ch,a)==0)

{

fscanf(fk,"%k",ch);

printf("\t\t%s\t:\tkeyword\n",a);

flag=1;

}

fscanf(fk,"%s",ch);

}

rewind(fk);

if(flag==0)

{

 if(isdigit(a[0]))

  printf("\t\t%s\t:\tconstant\n",a);

 else

  printf("\t\t%s\t:\tidentifier\n",a);

}

flag=0;

fscanf(fi,"%s",a);

}

}

   OUTPUT: