Please add comments with the code to explain the functions

2. (40 points) Write a program to check if an input is a valid hashtag (starts with #, contains only letters, numbers, and underscore, no space or special characters). 1) Name your program hashtag.c. 2) The user input ends with the user pressing the enter key (a new line character). 3) Library function isalpha(), isdigit(), and isalnum() are not allowed in this program. 4) Use getchar() to read in the input. Example input/output: Input: #cseUSF Output: It is a valid hashtag Input: #TBTimes Opinion Output: It is a valid hashtag Input: #933FLZ Output: It is a valid hashtag Input: #60 Minutes? Output: It is an Invalid hashtag