LL parsing

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
char prod [3][10]={"A->aBa","B->bB","B->@"};
char first[3][10]={"a","b","@"};
char follow[3][10]={"$","a","a"};
char table[3][4][10];
char input[10];
int top=-1;
char stack[25];
char curp[20];
push(char item)
{
        stack[++top]=item;
}
pop()
{
        top=top-1;
}
display()
{
        int i;
        for(i=top;i>=0;i--)
        printf("%c",stack[i]);
}
numr(char c)
{
        switch(c)
        {
                case'A':return 1;
                case'B':return 2;
                case'a':return 1;
                case'b':return 2;
                case'@':return 3;
       }
return(1);
}
void main()
{
        char c;
        int i,j,k,n;
        for(i=0;i<3;i++)
        for(j=0;j<4;j++)
        strcpy(table[i][j],"e");
        printf("\nGrammar\n");
        for(i=0;i<3;i++)
        printf("%s\n",prod[i]);
        printf("\nfirst={%s,%s,%s}",first[0],first[1],first[2]);
        printf("\nfollow={%s%s}\n",follow[0],follow[1]);
        printf("\nPredictive parsing table for the given grammar\n");
        strcpy(table[0][0],"");
        strcpy(table[0][1],"a");
        strcpy(table[0][2],"b");
        strcpy(table[0][3],"$");
        strcpy(table[1][0],"A");
        strcpy(table[2][0],"B");
        for(i=0;i<3;i++)
        {
                k=strlen(first[i]);
                for(j=0;j<k;j++)
                if(first[i][j]!='@')
                strcpy(table[numr(prod[i][0])][numr(first[i][j])],prod[i]);
                else
                strcpy(table[numr(prod[i][0])][numr(follow[i][j])],prod[i]); 
        }
        printf("\n------------------------\n");
        for(i=0;i<3;i++)
        
        for(j=0;j<4;j++)
        {
                printf("%-10s",table[i][j]);
                if(j==3) printf("\n-------------------\n");
        }
        printf("enter the input string terminated with $ to parse:-");
        scanf("%s",input);
        for(i=0;input[i]!='\0';i++)
        if((input[i]!='a')&&(input[i]!='b')&&(input[i]!='$'))
        {
                printf("invalid string");
                exit(0);
        }
        if(input[i-1]!='$')
        {
                printf("\n\nInput String Entered Without End Marker $");
                exit(0);
        }
        push('$');
        push('A');
        i=0;
        printf("\n\n");
        printf("stack\t Input\taction");
        printf("\n----------------------------\n");
        while(input[i]!='$'&&stack[top]!='$')
        {
                display();
                printf("\t\t%s\t",(input+i));
                if(stack[top]==input[i])
                {
                        printf("\tmatched %c\n", input[i]);
                        pop();
                        i++;
                }
                else
                {
                        if(stack[top]>=65&&stack[top]<92)
                        {
                                strcpy(curp,table[numr(stack[top])][numr(input[i])]);
                                if(!(strcmp(curp,"e")))
                                {
                                        printf("\ninvalid string-Rejected\n");
                                        exit(0);
                                }
                                else
                                {
                                        printf("\tapply production %s\n",curp);
                                
                                        if(curp[3]=='@')
                                        pop();
                                        else
                                        {
                                                pop();
                                                n=strlen(curp);
                                                for(j=n-1;j>=3;j--)
                                                push(curp[j]);
                                        }
                                 }                                 
                        }
                 }
          }
          display();
          printf("\t\t%s\t",(input+i));
          printf("\n--------------------\n");
          if(stack[top]=='$'&&input[i]=='$')
          {
                printf("\n valid string- Accepted\n");
          }
          else
          {
                printf("Invalid string-Rejected\n");
          }
}