Strongly recommend to minimize the browser and try this yourself first.
This is a simple trick question. Since putchar() prints a character, we need to call putchar() for all digits. Recursion can always be used to replace iteration, so using recursion we can print all digits one by one. Now the question is putchar() prints a character, how to print digits using putchar(). We need to convert every digit to its corresponding ASCII value, this can be done by using ASCII value of ’0′. Following is complete C program.
One important thing to note is the sequence of putchar() and recursive call print(n/10). Since the digits should be printed left to right, the recursive call must appear before putchar() (The rightmost digit should be printed at the end, all other digits must be printed before it).
from : www.geeksforgeeks.com