S6 CSE COMPILER LAB : DFA TO ACCEPT IDENTIFIERS IN C LANGUAGE

/*  DFA TO ACCEPT IDENTIFIERS IN C LANGUAGE  */

        

#include<stdio.h>

#include<string.h>

void main()

{

        char id[20],s,p,q,r;

        int l,i;

        s=p;

        printf("Enter the input:");

        gets(id);

        if((s==p)&&(((65<=id[0])&&(id[0]<=90))||((97<=id[0])&&(id[0]<=122))||(id[0]==95)))

              s=q;

        else

              s=r;

        l=strlen(id);

        for(i=1;i<l;i++)

        {

            if((s==q)&&(((65<=id[i])&&(id[i]<=90))||((97<=id[i])&&(id[i]<=122))||(id[i]==95)||((48<=id[i])&&(id[i]<=58))))

                    s=q;

            else

                    s=r;

        }

        if(s==q)

             printf("Input is a Valid identifier\n");

        else

            printf("Input is Not an identifier\n");

}

OUTPUT

Enter the input:abc

Input is a Valid identifier

Enter the input:2abc

Input is Not an identifier

Enter the input:abc2

Input is a Valid identifier

Enter the input:123

Input is Not an identifier

Enter the input:ab_c

Input is a Valid identifier