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Hello all this is Section 7 of PLCC programming from scratch.

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And now we're going to start getting into our actual process logic which is really the heart and soul

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of a C program.

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Before we get started throwing logical blocks all over ladders we need to stop.

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And this is the part we really think about what we're about to program and visualize the process.

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What does this machine look like.

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How does it work.

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How is it laid out.

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Where did the process engineer have in mind when he created the piano idea that we're looking at.

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And if you don't know what a piano ideas it's piping an instrument diagram which is a typical engineering

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output for any type of pipe system.

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So before we start programming how do we imagine the process.

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How do we understand the process and visualizing the process with something like a visual flow diagram

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a cause and effect chart or even a Vizio diagram is a really helpful tool in knowing what your program

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is going to need to look like how to divide it up between various ladders.

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And really the more you can envision the process from the beginning the easier your program will be

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to right.

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There's a saying that writing clarifies thought and it's true when we look at the document on the screen

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.

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It's nothing elaborate.

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It's nothing too highly structured.

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It's a simple Excel spreadsheet but it tells us in time exactly what needs to happen and when when we're

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starting up a system and it's hugely important to have something like this in front of you when you're

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writing a C program.

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A lot of us can do it off the top of our head and we get a little cocky about doing that.

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And more times than not we spend far more time than we should shaking down and debugging a program before

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we can load it onto a machine and hand it off to somebody.

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And another thing we need to consider when we're putting process logic into a program is what are the

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contingencies what can go wrong if we're in the middle of a start up and all of a sudden an alarm condition

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arises do we interrupt the start up do we sound the alarm and keep going.

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What needs to happen what can happen all the way through our process.

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Murphy's Law says anything that can happen will happen.

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And in the world of process and automation that's very true.

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If it's possible for somebody to throw a shoe into your water tank it will happen.

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And when that shoe blocks your discharge valve What is your PEOC going to do about it.

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You have to think about not only how is the machine designed.

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How is the machine supposed to run but what things can happen along the way and how are we going to

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handle those exceptions for the type of programs we're riding in this course.

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Very simple.

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One or two elements systems of visual flow diagram probably is necessary but in a real world scenario

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when you're called to use APL c you're more than likely going to be controlling 10 to 20 or more different

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devices.

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And on top of that receiving inputs from just as many there aren't many people who can keep that many

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different variables straight in their head.

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So if you can get as many diagrams as many flowcharts as many theories of operation written out and

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on your desk in the beginning it's going to make your job programming a lot faster a lot easier and

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certainly a lot cleaner.