Prerequisites: Control Systems Overview

---

Lesson 1: Getting Started

If you want to tell a computer to do something, you have to communicate with the computer in a programming language. When we say language, we mean it. A language has words and grammar and everything else, just like French.

Computers, despite what you may think, are dumb. They do only exactly what you tell them to, and don't guess or interpret. If say to your Mom or Dad "Hey, can you bring me that thing?", there's a (slim) chance they may bring you the right "thing". A computer wont. Ever. Just a cold, unfeeling "ERROR". A programming language is very precise, and to tell a computer what you want, you have to be precise too. In this training session, we'll introduce programming to you, and make some things work. You know, those things.

Hang on, it gets harder from here.

(A quick note...If you know all this already and are getting bored...CONGRATULATIONS! Here's a ​link to some cute corgi puppy videos as your reward. Then, come back and dive into a later section. This is all self-paced.)

We'll be starting with a programming language called ​Python, specifically Python 3. There are a lot of programming languages. Some are created because they're better for solving certain problems, others because people are bored and want to try something new. Python has been around for a while, and its pretty popular because its easy to use. The team uses Java to control the robot but that language is a little trickier. We'll get to that one later once you get a handle on the basics.

Python, like every programming language, has a structure. Here are the big parts:

• Variables: Things you assign to and read from. Like in Algebra. A="Dump Truck" sets the variable A to the string "Dump Truck". They're basically the nouns.
• Functions: These do things. They take nouns as arguments, do something, and can return nouns. In redCar = paintCarRed(blueCar), paintCarRed is a function. They're the verbs, they do things, and they take variables and return variables.
• Control Structures: These are instructions like IF this is true THEN do that…. These are like grammar rules, like use active voice, or use punctuation.
• Libraries: A lot of other people have written functions to do things. A lot of things. When these things are bundled together they're called libraries. You can tell a computer to use a library and save your self a lot of typing.

Much like in English, you blend all of these together to create stories, or programs. Both have a beginning middle and end. So lets write the first programming story that all programmers start with: "Hello World"

a="Hello World"
print(a)

This tells the computer to print, you guessed it, "Hello World" on the screen.

Now you try it: Go ​here. Its our code editor for this training exercise. You can enter code in the center area of the page, click execute, and see the results below. I recommend you bookmark that site, its pretty cool. Now on that site, highlight all the text in the central area and hit back space (this we'll clear out all the sample code. We'll call this "clear out the test code" from now on. Then highlight the code above, and click copy, and paste the two lines above into that editor. Then click "Execute". (We'll call this series of actions "run the code" from now on. After a bit, you'll be rewarded with the message in the bottom window:

Hello World!

And, boom, now you're a programmer. The rest is just more details. This is the end of Lesson 1.

Lesson 2: More Things To Do

Now "Hello World" is not too exciting if you want to program robots, but its important. It is a program, albeit a short one. We showed you how to run a function (or verb) print, which does something with its argument A, where A is assigned the value "Hello World".

If you want to do more, we need to introduce control structures. Take the program below.

Location = 'HERE'

IF (location == 'HERE') THEN

Print "We're here! Come on in'

ELSE

Print "Go away, we're out eating tacos"

ELSEIF

Cut and paste this program here, then run it (Press Execute). It should print "We're here! Come on in!". If it doesn't ask for help. Spacing matters in Python.

Now, change line one to Location='Poughkeepsie, NY'. It should print "Go away, we're out eating tacos". If I was in Poughkeepsie, I'd be out eating tacos too. Ummm, tacos.

This control struction evaluates a *expression* (location=='HERE') and if its true, then do the THEN part, otherwise do the ELSE part. This is called the IF-THEN-ELSE structure, and it’s the most basic control structure.

Here's a couple other control structures that you should know

For Loop: This one repeats over a variable. It's good for counting try running this one:;

For (Potato

While: The more charming cousin of the for loop, this one repeats

---

Programming Archive?