problem 1:

describe, in detail, an algorithm which will draw a one-pixel wide outline of a circle of integer radius centered on the origin.

problem 2:

describe the modifications needed to your algorithm in part (1) to make it draw a filled circle.

problem 3:

describe the modifications needed to your algorithm in part (1) to make it draw the outline of a circle centered at arbitrary integer coordinates.

problem 4:

describe the modifications needed to your algorithm in part (3) to make it draw the outline of a circle centered at arbitrary non-integer coordinates and of non-integer radius.