Source code in the freebasic programming language

' version 15-10-2016
' compile with: fbc -s gui

' Variant with Integer-Based Arithmetic from Wikipedia page:
' Midpoint circle algorithm
Sub circle_(x0 As Integer, y0 As Integer , radius As Integer, Col As Integer)

  Dim As Integer x = radius
  Dim As Integer y
  ' Decision criterion divided by 2 evaluated at x=r, y=0
  Dim As Integer decisionOver2 = 1 - x

  While(x >= y)
    PSet(x0 + x, y0 + y), col
    PSet(x0 - x, y0 + y), col
    PSet(x0 + x, y0 - y), col
    PSet(x0 - x, y0 - y), col
    PSet(x0 + y, y0 + x), col
    PSet(x0 - y, y0 + x), col
    PSet(x0 + y, y0 - x), col
    PSet(x0 - y, y0 - x), col
    y = y +1
    If decisionOver2 <= 0 Then
      decisionOver2 += y * 2 +1 ' Change in decision criterion for y -> y +1
    Else
      x = x -1
      decisionOver2 += (y - x) * 2 +1  '  Change for y -> y +1, x -> x -1
    End If
  Wend

End Sub

' ------=< MAIN >=------

ScreenRes 600, 600, 32
Dim As Integer w, h, depth
Randomize Timer

ScreenInfo w, h

For i As Integer = 1 To 10
  circle_(Rnd * w,  Rnd * h , Rnd * 200 , Int(Rnd *&hFFFFFF))
Next


'save screen to BMP file
BSave "Name.BMP", 0


' empty keyboard buffer
While Inkey <> "" : Wend
WindowTitle "hit any key to end program"
Sleep
End