From Breadboard to Circuit Board – Creating the Logic


In my last article, I explained how logic gates work.  In this article I want to explain how we use them to process information.  This will be a very basic discussion.  There is a LOT more actually going on, but hopefully this will give you a little more insight into what is going on inside your computer.

Let's use a simple example.  Remember I said that we built a simple computer when I was in college.  It was basically a calculator or clock display.

It's been over 30 years ago, so my memory may be off a little.  What sticks with me is the basics, so that's what I'll give you here.

We had switches for inputs.  These were just like little light switches.  We could turn them on and off.  They were connected to wires which were then connected to the logic gate chips on the other end.

For output, we had a display like a digital clock.

Screen Shot 2019-01-10 at 9.57.22 AM

Our job was to get the switches that we turned on and off to show the numbers on the output.  We had one display per digit and we could put them in a series to produce a multi-digit number.

So, if I switched on the first switch, it should turn on the right two bars on the display producing what we know as a 1.

If we switched the second switch on, then we wanted what looked like a 2 on the display - the top bar, the top right bar, the middle bar, the left bottom bar, and the bottom bar, would make a 2.

We went through the digits deciding which bars needed to be turned on to show us which switches were turned on.

The output clock display had pins that we could connect a wire to for each bar in the display.

If my first switch was on, I should have it wired to both the right bars so that they would come on.  If this were my only switch and only wanted the one number to appear on the output, I could just use the direct connection from my switch to the pins to produce the 1 on the display.

But, since I wanted other switches to turn on the same led bar, I would need to use logical gates to decide when each bar should be turned on.

For the number 2 I needed 5 bars turned on.  One of those would also be turned on for the 1 - the top right bar.  So, that bar would need a connection from both the 1 switch and the 2 switch so that it would be turned on if either of those switches were on.

Using an OR gate, I could hook my 1 switch and my 2 switch to the OR gate inputs and attach the OR gate output to the top right bar pin.  Then if either of those switches are turned on, the right top bar would display.

Screen Shot 2019-01-10 at 10.18.14 AM

Again, this is extremely simplified to make my point and there are a lot more chips involved.  To see a real, technical explanation of everything going on, check out this article.

My point in this article is to explain how the computer chips use logic and binary to make the computer process data.  And how everything inside the computer all boils down to 1's, 0's, AND's, OR's, NOT's and XOR's underneath.

The logic gates are used to process the information from the input(s) so that it can send out the intended information to the output.

The logic gate actually lives in a computer chip.  Computer chips today have many logic gates inside.  Different computer chips are made to do many different things and they are internally wired on circuit boards to do those things.

In my mind, this is the foundation of what makes the computer work.  There are also clocks that keep things working in sequence.  And it's hard to count without some way to 'remember' what the last number was.

Have you ever counted and lost your place?  Your brain has to remember where you were last to get to the next number.  So do computers.

We'll talk about Memory next.


The technology to make these computer chips have allowed the chips to get smaller and smaller and smarter and smarter.

Circuit boards are used and the connections are soldered instead of using wires and breadboards.  The breadboards are used to make the prototypes and then once they have it working correctly, they make the connections on a circuit board.

But, inside of all those chips, what we discussed above is going on many, many times per second.  Your input device sends a signal to the processor which makes a decision based on the logic gates and how they are connected inside.

So, basically, it all boils down to 1', 0', and logic gates.

It is so amazing to me that something that simple can be built upon again and again to produce the computers we hold in the palm of our hand which do so much.  Many of us could not live without our electronic, computerized devices anymore.

When my kids were younger and playing video games and would complain about the graphics, I would think, "If they only knew what all it took to get those graphics as good as they are!"

And when I see the graphics we have today, which are so realistic, and the amount of processing that goes on before I can even blink my eye, I am amazed at everything that is going on behind the scenes that we don't even think about.

Just the technology behind what I'm doing now... something as simple as typing up this blog post... is totally amazing when you stop and think about everything that is actually happening behind the scenes.

It's a wonderful time in this world that we live in, when technology is changing faster than we can blink.  I've watched it come from mostly nothing to something so large, fast and amazing that it baffles the mind.

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