Can anyone help me with this

I am a blind guy who wants to create a program that will read the text on the screen out loud in my native language. I already use english-based screen readers which can read text out loud in english.

My question is if I want to create text-to-speech program, will I have to use a large dictionary that will hold the alphabet in one side and the spoken version mp3 as its value in another side. As an example, will I have to create a dictionary like "a" : "a.mp3" something like that?

And whenever the program encounters "a" or any letter in the dictionary the program will play the sound that is associated with it? are text-to-speech programs built like this or there is an easier way?

thank you in advance.