Draw a circle in a grid

I have following diagram

I have divided this 100*100 space in 36 grids..6 grids in each row.How could I draw a circle by taking 4 square grids..like

Answer 1

[Chad Greene]

This function draws circles easily.

Answer 2

[Image Analyst]

You should know the circle center locations and radii. Then it's a simple matter of using one of the code snippets from the FAQ: http://matlab.wikia.com/wiki/FAQ#How_do_I_create_a_circle.3F