Part I: The first two commands
that create curves are ARCR (means ARC to the Right ) and ARCL (means
ARC to the Left). The two numbers that follow the commands indicate
the degree and the diameter of the arcs drawn.
This is the
pictures of the practice exercises: 
The first picture (E1) show a quarter of a circle of radius 50
pixels and hence the diameter is 100 pixels. Since there are 360
degrees in a whole circle, there are 90 degrees in that arc and thus
the first command will be ARCR 90 100 RT 90 FD 50 RT 90 FD 50.
USE the commands ARCR, ARCL and FD to turn the red pictures into black.
Load practice exercises: (Click on e1, e2 to get the pictures in seelogo)
After you practice load the first set of exercises. You may need to use also the RT and JT commands with them.
Part II: The next two commands are CURVER and CURVEL. Like
the ARCR and ARCL commands they need to be followed by two numbers
where the first number defines the degrees of the arc. The second
number defines the length of the cord of the arc. For example: the
following arc was created using the command CURVER 120 40 
Picture of the curve examples E1 &
E2: 
In the first example E1 all the distances are the same (30
pixels) and the degrees of the three curves are 270, 180 and 90. Thus
the command that makes the picture is:
CURVER 270 30 CURVEL 180
30 CURVER 90 30
In the second example E2 the distances change but
all the degrees are the same (120) and thus the answer is:
CURVER
120 60 CURVEL 120 40 CURVER 120 20
additional Exercises (Use Curver, CurveL and other commands)