DFA
#include <stdio.h>
#include <string.h>
int main()
{
    char a[10];
    printf("As the expression has to end with 01 as a substring it has 3 states 0,1,2\n");
    printf("Enter the expression to be checked:\n");
    scanf("%[^\n]s",a);
    printf("%s\n",a);
    int state = 0;
    for (int i=0; i<strlen(a);i++){
        if(state==0 && a[i]=='1'){
            state = 0;
        }
        else if(state==0 && a[i]=='0'){
            state = 1;
        }
        else if(state==1 && a[i]=='0'){
            state=1;
        }
        else if(state==1 && a[i]=='1'){
            state = 2;
        }
        else if(state==2 && a[i]=='0'){
            state = 1;
        }
        else if(state==2 && a[i]=='1'){
            state = 1;
        }

    }
    if(state==2){
        printf("The expression is accepted as it reached the final state 2");
    }
    else{
        printf("The expression is rejected as it didn't reach the final state, it is in state %d",state);
    }
    return 0;
}

NFA

#include <stdio.h>
#include <string.h>

int main()
{
    char a[10];
    printf("Enter the input string:\n");
    scanf("%[^\n]s",a);
    int state = 0;
    int i = 0;
    int len = strlen(a);

    while(i < len){
        if(state == 0 && a[i] == '0'){
            state = 0;
        }
        else if(state == 0 && a[i] == '1'){
            state = 1;
        }
        else if(state == 1 && a[i] == '0'){
            state = 1;
        }
        else if(state == 1 && a[i] == '1'){
            state = 2;
        }
        else if(state == 2 && a[i] == '0'){
            state = 0;
        }
        else if(state == 2 && a[i] == '1'){
            state = 2;
        }

        i++;
    }

    if(state == 2){
        printf("The input string is accepted as it reached the final state 2.and ending with 11\n");
    }
    else{
        printf("The input string is rejected as it didn't reach the final state, it is in state %d.\n", state);
    }

    return 0;
}

FIRST
#include <stdio.h>
#include <string.h>
#include <ctype.h>

int num_nt;
char nt[10];
int p[10];
char productions[10][10][10];

void find_first(char non_t) {
    for (int i = 0; i < num_nt; i++) {
        if (nt[i] == non_t) {
            for (int j = 0; j < p[i]; j++) {
                char first = productions[i][j][0];
                if (isupper(first)) {
                    find_first(first);
                } else {
                    printf("%c ", first);
                }
            }
        }
    }
}

int main() {
    printf("Enter number of non-terminals:\n");
    scanf("%d", &num_nt);
    printf("Enter non-terminals:\n");
    for (int i = 0; i < num_nt; i++) {
        scanf(" %c", &nt[i]);
    }

    for (int i = 0; i < num_nt; i++) {
        printf("Enter the number of productions for %c: ", nt[i]);
        scanf("%d", &p[i]);
        printf("Enter the productions for %c:\n", nt[i]);
        for (int j = 0; j < p[i]; j++) {
            scanf("%s", productions[i][j]);
            printf("\n");
        }
    }

    for (int i = 0; i < num_nt; i++) {
        printf("First ( %c ): ", nt[i]);
        find_first(nt[i]);
        printf("\n");
    }
    return 0;
}

SYMBOL TABLE
#include<stdio.h>
#include<ctype.h>
#include<stdlib.h>
#include<string.h>
#include<math.h> void
main()
{
int i=0,j=0,x=0,n; void *p,*add[5];
char ch,srch,b[15],d[15],c;
printf("Expression terminated by $:");
while((c=getchar())!='$')
{
b[i]=c;
i++;
}
n=i-1;
printf("\nGiven Expression:");
i=0;
while(i<=n)
{
printf("%c",b[i]);
i++;
}
printf("\n\nSymbol Table\n\n");
printf("Symbol \t addr \t\t type");
while(j<=n)
{
c=b[j];
if(isalpha(toascii(c)))
{
p=malloc(c);
add[x]=p; d[x]=c;
printf("\n%c \t %d \t identifier\n",c,p);
x++; j++;
}
else
{
ch=c;
if(ch=='+'||ch=='-'||ch=='*'||ch=='=')
{
p=malloc(ch);
add[x]=p; d[x]=ch;
printf("\n%c \t %d \t operator\n",ch,p);
x++; j++;
}
}
}
}

PDA
#include<stdio.h>
#include<string.h>
int top;
char s[10];
void push(int x)
{
  s[top++]=x;
}
void pop()
{
  top--;
}
int main()
{
  int i,n,state=0;
  char a[10];
  printf("Program For PDA Which Accpets Strings Of (a^n)(b^n)\n");
  printf("Enter String:");
  gets(a);
  n=strlen(a);
  top=-1;
  for(i=0;i<n;i++)
  {
    if(a[i]=='a' && state==0)
    {
      push(a[i]);
      state=0;
    }
    else if(a[i]=='b' && state==0)
    {
      pop(a[i]);
      state=1;
    }
    else if(a[i]=='b' && state==1)
    {
      pop();
      state=1;
    }
    else
    {
      break;
    }
  }
  if(a[i]=='\0' && top==-1 && state==1)
    state=100;
  if(state==100)
    printf("String Accepted.");
  else
    printf("String Rejected.");
  return 0;
}