Above and below the main section
of breadboard are two horizontal rows of
sockets, each divided in the middle. These
horizontal rows (often called “rails” or
“buses”) will be used to carry +5 volts (Vdd)
and Ground (Vss). Our preparation of the
breadboard involves connecting the rails so
that they run from end-to-end, connecting the
top and bottom rails together and, finally,
connecting the rails to Vdd and Vss. If we XRayed
the breadboard, we would see the
internal connections following the Figure 4-2.