How to implement 10 PRINT

Continuing the series, this article demonstrates how to implement ’10 PRINT’ to create interesting line images. 10 PRINT is an old Commodore 64 one-line program written in BASIC that looks like this:

10 PRINT CHR$(205.5+RND(1)); : GOTO 10

For more information, see

For the previous entry in the series, see this page: How to use shapes, placements, and colors

Here is the code to implement 10 PRINT:

x = 0
y = 0
spacing = 10
rand_point = 0.50

def setup():
    size(400, 400)
    # stroke('#2C4AF0')  # blue
    # stroke('#106A09')  # green
    # stroke('#611ED6')  # purple
    # strokeWeight(3)

def draw():
    global x, y, spacing, rand_point
    if (random(1) < rand_point):
        line(x, y, x+spacing, y+spacing)
        line(x, y+spacing, x+spacing, y)
    x += spacing

    if x > width:
        x = 0
        y += spacing


Notes about this code:

  • The draw() function in acts like a continuous loop, similar to a Pygame main event loop
  • The spacing variable controls the length of the diagonal lines
  • The background() variable controls the color of the background
  • The stroke() variable controls the color of the lines
  • The strokeWeight() variable controls the thickness of the lines
  • The rand_point is the sorting point at which each random number that is generated will be rendered as either a forward slash or a back slash.

By playing with all of these variables, it is possible to create a wide variety of outputs. For example:

A wide variety of outputs can be achieved.

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