Can anyone please tell me if I can use different font sizes in output screen
For the console?
Nope.
-Albatross
You can do this manually. Right click on the top left corner of your console window and set a font size from the properties menu.
I think Albatross meant there is no way to control this font size from your program. If this is what you're hoping to do, see Albatross' answer.
I want to display fonts of different size at the same time in the output screen.
No way to do this in the console. Console isn't meant for being pretty, it is just meant to write and read basic (text) data.