why there are 2 sections having 20 ports in a breadboard?

Question

In a breadboard there are 2 sections; one in which the points/ports are at same potential vertically.But in the 2nd section the points are at same potential horizontally.And it has 2 such parts for both.

Answer 1

The horizontal points are for common power and ground. Power is usually +5 volts and 'ground' is 0 volts return current for the +5v. Make sure all your logic ICs are 5V logic, or at least all the same (might be +3.3V). If the IC logic power voltage is 3.3 V, then use 3.3V on the horizontal.

Since every IC on the board needs power and ground, it's easier to make a small jumper wire from the proper vertical port to the horizontal port.

If you are breadboarding linear ICs (Op Amps) but no logic ICs, then you can use the horizontal lines for +12V and -12V, instead of +5V and ground.

Answer 2

I've used numerous different breadboards over a span of more than 40 years and have no idea what a "port" is. Don't you really mean connection points? Most breadboards (for integrated circuits) allow the IC to be inserted so that it straddles the long axis of the breadboard. Each IC pin inserts into the innermost contact of a row of 5 contacts, arranged at right angles to the long axis of the board. Thus, each IC pin now has 4 empty contact points where components and wiring can be connected. In addition, some models include 2 or 3 columns of contacts which run the full length of the long axis. These are used for power and ground, which must be connected to each IC. The long power contact strips are not necessarily on every breadboard, but they sure are handy!

I've used a lot of imagination, here. I hope I've answered your intended question.....................

Answer 3

The row across the top or bottom is usually used for a power buss. I usually put all the connections to positive power on the top row, and ground on the bottom row.