As stated earlier, a canvas exists only in your computer's memory. It gets realized only when this is printed to a terminal. This - in most cases - is not done automatically. You have to explicitely print a canvas to a terminal.
A terminal can be different things: an x11-window on your screen, a graphics file (png, eps, pdf), or a postscript-like file (blopeps), which is the native terminal of blop, all others are based on this. Existing terminals: