Compiler Design Lab

For 'C' Compiler click the link given below

/******************************************************************************

1. Write a C program to identify whether a given line is a comment or not.

*******************************************************************************/

#include<stdio.h>

#include<conio.h>

void main()

{

    char com[30];

    int i=2,a=0;

    clrscr();

    printf("\n Enter comment:");

    gets(com);

    if(com[0]=='/')

    {

        if(com[1]=='/')

    printf("\n It is a comment");

    else if(com[1]=='*')

    {

        for(i=2;i<=30;i++)

        {

            if(com[i]=='*'&&com[i+1]=='/')

            {

                printf("\n It is a comment");

                a=1;

                break;

               

            } else continue;

           

        }

        if(a==0)

        printf("\n It is not a comment");

       

    } else printf("\n It is not a comment");

       

    } else printf("\n It is not a comment");

    getch();

   

}

______________________________________________________________________________________________

******************************************************************************

2. Write a C program to recognize strings under 'a', 'a*b+', 'abb'.

*******************************************************************************/

#include<stdio.h>

#include<conio.h>

 #include<string.h>

#include<stdlib.h>

 void main()

{

char s[20],c;

int state=0,i=0;

clrscr();

printf("\n Enter a string:");

gets(s);

while(s[i]!='\0')

{

switch(state)

{

case 0: c=s[i++];

 if(c=='a') state=1;

else if(c=='b')

state=2;

else state=6;

break;

case 1: c=s[i++];

if(c=='a')

 state=3;

else if(c=='b')

state=4;

else

state=6;

                break;

case 2: c=s[i++];

 if(c=='a') state=6;

else if(c=='b')

state=2;

 else state=6;

break;

 case 3: c=s[i++]; if(c=='a')

state=3;

else if(c=='b')

state=2;

else

state=6;

break;

case 4: c=s[i++];

                if(c=='a')

 state=6;

else if(c=='b')

state=5;

else state=6;

break;

case 5: c=s[i++];

if(c=='a')

state=6;

else if(c=='b')

state=2;

else

state=6;

break;

case 6: printf("\n %s is not recognised.",s);

exit(0);

} }

if(state==1)

printf("\n %s is accepted under rule 'a'",s);

else if((state==2)||(state==4))

printf("\n %s is accepted under rule 'a*b+'",s);

else if(state==5)

printf("\n %s is accepted under rule 'abb'",s); getch();

}

***************************************************************************************
3. Write a C program to test whether a given identifier is valid or not
****************************************************************************************

#include<stdio.h>
#include<conio.h>
#include<ctype.h>
void main()
{
    char a[10];
    int flag,
    i=1;
    clrscr();
    printf("\n Enter an identifier:");
    gets(a);
    if(isalpha(a[0]))
    flag=1;
    else
    printf("\n Not a valid identifier");
    while(a[i]!='\0')
    {
        if(!isdigit(a[i])&&!isalpha(a[i]))
        {
            flag=0; break;
           
        } i++;
       
    }
    if(flag==1)
    printf("\n Valid identifier");
    getch();
   
}


***************************************************************************************
4. Write a C program to simulate lexical analyzer for validating operators.
****************************************************************************************

#include<stdio.h>
#include<conio.h>
void main()
{
    char s[5];
    clrscr();
    printf("\n Enter any operator:");
    gets(s);
    switch(s[0])
    {
        case'>':
        if(s[1]=='=')
        printf("\n Greater than or equal");
        else printf("\n Greater than");
        break;
        case'<':
        if(s[1]=='=')
        printf("\n Less than or equal");
        else
        printf("\nLess than");
        break;
        case'=':
        if(s[1]=='=')
        printf("\nEqual to");
        else printf("\nAssignment");
        break;
        case'!':
        if(s[1]=='=')
        printf("\nNot Equal");
        else printf("\n Bit Not");
        break;
        case'&':
        if(s[1]=='&')
        printf("\nLogical AND");
        else
        printf("\n Bitwise AND");
        break;
        case'|':
        if(s[1]=='|')
        printf("\nLogical OR");
        else
        printf("\nBitwise OR");
        break;
        case'+':
        printf("\n Addition");
        break;
        case'-':
        printf("\nSubstraction");
        break;
        case'*':
        printf("\nMultiplication");
        break;
        case'/':
        printf("\nDivision");
        break;
        case'%':
        printf("Modulus");
        break;
        default:
        printf("\n Not a operator");
       
    }
    getch();
   
}