Setting Resolution in Raspberry Pi for HD TV : from a non IT person

I connected my raspberry Pi ( Raspbian  OS)  with HD LED 42 inch TV and with few modifications  in config.txt,  I could run the raspberry pi with full 1920 x 1080 full resolution.  However the fonts were small in terminal and at other places


The fonts in terminal and other menu items can be easily changed from appearance settings
 which are available at right click

1. right click on desktop as desktop preferences  
2. edit tab in terminal
3.  change geometry with right click on panel settings
4. web can be managed by ctrl + or ctrl -

Still programs like scratch 1.4 Sonic pi and Mathematica  fonts were too small and difficult to read at a distance of  8-10 feet from TV. So  my journey to correct these started. After numerous website searches,  comment on following two statements in config.txt was removed


framebuffer_width=1280
framebuffer_height=720


It corrected web and sonic pi to a large extent,  but Scratch and Mathematica remained a problem.

As I understood somehow I need to lower the resolution on the fly or without restart which has to be done before starting X  ( X seems to GUI  name ) so that i can still boot to different resolution if i want


so  this command before start x did the trick

fbset -g 800 450 800 450 16

The scratch and mathematica fonts are now visible from 10 feet.

 when you are not using scratch  startx without fbset command and you are good with original resolution.