C language

Write a function whisper that changes every uppercase letter to a lowercase letter. that does not use a loop counter but instead uses pointer arithmetic.r. It should implement the following specification:

/* Writes the message of msgIn into msgOut , except with all

* lowercase letters . Returns 0 if successful and -1 if

* either of msgIn or msgOut is NULL . */

int whisper ( char * msgIn , char * msgOut );