How to print next letters until Z and continue to A?

Question

This code prints the next letters of what I input. For example, I input "v", it will show vwxyz, but I want it to print the others too, like vwxyzabc.....

int main()
{
   char a;
   int flag = 0;
   scanf("%c", &a);

   while (a <= 'z') 
   {
      printf("%c", a);
      a++;
   }

   printf("\n");
   return 0;
}

I am new to c++, can someone help me?

Answer 1

If the incremented character is not an alphabet, deduct 26 to go back to the starting and do the loop until you see the entered character.

#include <cctype> // std::isalpha

char curr = a;
do
{
   printf("%c", curr);
   ++curr;
   if (!std::isalpha(static_cast<unsigned char>(curr)))
      curr -= 26;

} while (curr != a);

(See live demo)