Printing with variable font sizes.

Hai,
Please tell me how I can perform the following tasks. I have a dot matrix printer and I wish to do the following
1. While printing a line of text I want to increase the character size.
2. Similarly I want ot decrease the character size during printing.
3. After performing any of the above tasks I wish to return to normal character size.
4. How can I advance half a line. Say for example to print a subscript.
5.can default tab size be set.