both are same.  a[i] is treated as *(a+i), and i[a] is *(i+a).  And from the rule of associativity, we can see that both expressions will yield to the same result.

int main ()
{   int i,j,k;
  for(i=1;i<4;i++)
  {     for(j=1;j<4;j++)
    {       for(k=1;k<4;k++)
      {         if((i!=j) && (j!=k) && (i!=k))
        {           printf("%d%d%dn",i,j,k);
        }}}}}

heap memory used for dynamic memory allocation using malloc,realloc,new etc
global and static variable are stored in data segment.

String is a collection of charecter,it must be ended with null.
Charecter array is aset of elements if you didn't give a space for null,it shows error.

The size of the structutre will be the total size of fields holded by that structure.

There are various things to be observed for this
1. First of all while at the time of storing
      single character is stored as char abc = 's';
         where as string having single character can be stored as char pqr[] = "s";
2. single character takes one byte for storage
    String (even single character is stored) takes two bytes, one for one character and second for null character
    This can be verified by following C statement:
       printf("%d %d", sizeof(abc), sizeof(pqr));
    which gives output as 1 and 2 respectively. (assuming turbo C compiler and 1 byte for char)