Learn to Program with Small Basic

Let’s look at the computations. You calculate the total resistance (R tot
)
by adding the values of the three resistors together. Next, you calculate
the current (I ) that flows in the circuit by dividing the battery voltage (V )
by the total resistance. Then you calculate the voltage across each resistor
by multiplying the current by the value of that resistor. (Try reading
this paragraph aloud to your friends as if it’s super easy. It will blow their
minds!)
The following steps guide you through creating this program. So buckle
your seat belt, hold on tight, and get set to rocket into the exciting world of
computer simulations.
Step 1: Open the Startup File
To start creating this circuit simulator, open SeriesCircuit_Incomplete.sb from
this chapter’s folder. The file contains comments that tell you where to add
your code and empty placeholders for the subroutines you’ll write.
The folder for this chapter also includes the two background images
you’ll need: bkgndOff.bmp and bkgndOn.bmp (see Figure 12-5; we added the
image names for clarity). The two images are the same except for the state
of the switch: the switch is in the open position in bkgndOff.bmp but is closed
in bkgndOn.bmp.
bkgndOff.bmp
bkgndOn.bmp
Figure 12-5: The two background images of SeriesCircuit.sb
When you start writing the code for this program, you’ll see many hardcoded
numbers. These numbers represent the coordinate points for the
text boxes and labels and for checking the switch’s boundaries. To help you
understand where these numbers come from, refer to Figure 12-6. In this
figure, we added coordinate axes and gridlines on top of the background
image, and we marked the coordinates of all the points you’ll use in the
program.
172 Chapter 12