I showed him a C++ program I made that takes what you type in, then assigns values to each letter (A is the first letter in the alphabet so it gets the value of 1).. and so on. It then adds up all the values and tells you it. So the word "add" would have a value of 9.
I don't know what you should do with your dad. But:
If you did this all by yourself, starting from scratch, learning from books, in a month, it's damn impressive. And you did it in C++, which is one of the scariest programming languages in existence.
Seriously, thereThere are quite a few people out there taking interviews, seriously trying to get programming jobs, who would struggle with that. See this story.
I can only suggest: keep doing what you enjoy. Ignore your dad in this context; he doesn't know what he's talking about. You have talent in programming and willingness to learn - the main ingredients in becoming a great programmer.