tic tac toe game without any graphics programming

#include<stdio.h>
#include<string.h>
main()
{
    int a[3][3],m,i,j,k=1,r=0,b=1;
    char x[20],y[20];
    printf("               WELCOME   TO   TICTACTOE\n\n");
    printf("Enter the name of first player\n\n");
    scanf("                        %s",x);
    printf("\n\nEnter  the name of second player\n\n");
    scanf("                        %s",y);
    for(i=0;i<3;i++)
    {
        for(j=0;j<3;j++)
        {
            a[i][j]=k;
            k++;
        }
    }
     for(i=0;i<3;i++)
    {
        for(j=0;j<3;j++)
        {
            printf("                 %d",a[i][j]);
        }
        printf("\n\n\n");
    }
    printf("     >>The above matrix represents the positions of game<<\n");
    printf("       >>Inputs at the positons must be either 0 or 9<<\n");
    while(b!=0)
{
    r++;
    if(r%2==0)
    {
    printf("         >>plz enter the position Mr:%s<<\n",y);
    }
    else{
        printf("     >>plz enter the position Mr:%s<<\n",x);
    }
    scanf("%d",&m);
switch(m)
{
case 1:
    scanf("%d",&a[0][0]);
    break;
case 2:
    scanf("%d",&a[0][1]);
    break;
case 3:
    scanf("%d",&a[0][2]);
    break;
case 4:
    scanf("%d",&a[1][0]);
    break;
case 5:
    scanf("%d",&a[1][1]);
    break;
case 6:
    scanf("%d",&a[1][2]);
    break;
case 7:
    scanf("%d",&a[2][0]);
    break;
case 8:
    scanf("%d",&a[2][1]);
    break;
case 9:
    scanf("%d",&a[2][2]);
    break;
default:
    printf("plz enter the mentioned position\n");
}
     for(i=0;i<3;i++)
    {
        for(j=0;j<3;j++)
        {
            printf("                 %d",a[i][j]);
        }
        printf("\n\n\n");
    }
    if((a[0][0]==a[1][1]&&a[1][1]==a[2][2])||(a[0][2]==a[1][1]&&a[1][1]==a[2][0])||(a[0][0]==a[0][1]&&a[0][1]==a[0][2])||(a[1][0]==a[1][1]&&a[1][1]==a[1][2])||(a[2][0]==a[2][1]&&a[2][1]==a[2][2])||(a[0][0]==a[1][0]&&a[1][0]==a[2][0])||(a[0][1]==a[1][1]&&a[1][1]==a[2][1])||(a[0][2]==a[1][2]&&a[1][2]==a[2][2]))
   {
       printf("                          >>GAME OVER<<\n\n");
       b=0;
   }
}
   if(r%2==0)
   {
    printf("                               WINNER IS Mr:%s\n\n",y);
    printf("                               CONGRATULATIONS %s",y);
   }
   else
   {
    printf("                               WINNER IS Mr:%s\n",x);
    printf("                               CONGRATULATIONS %s",x);
   }

}

is my code good or not.plz comment.im a basic programmer who knows only c .and it is my trial