Accessing VDU Memory

hi u there,

I'm a newbie in C and I've a small little problem

question:

A program is to be written which would keep converting every capital letter on the screen to small case and every small case letter to the capital one. The procedure should stop the moment the user hits the key from keyboard.

The problem I'm facing is that how could I access the VDU memory......how could I got to those memory locations and work with them.....

I've searched and found that each charcter displyed on the screen occupies two bytes in VDU memory and the ascii value of the charcter present on zeroth row and zeroth column on the screen is stored at a location number 0xB000000.

there's one more query regarding this that I've found that it dosen't works with windows as windows handles the memory explicitly.


can anyone help me out for the logic of this program

ur help will be highly appreciated(I hope that this newbie would not be disappointed)

thanx in advance

bye