In the following pages, you'll be guided through a series of activities meant to introduce you to the basics of programming practice and vocabulary. If you've taken a computer science course, much of this may already be familiar to you! 

Here are some things you shouldn't worry about while you complete these activities:

1. Getting the "right" solution on the first try. What you should do is actively think about how your solutions change as you think about each problem differently.

2. Memorizing programming vocabulary. If this is your first time using programming parlance, don't worry about remember every particular term. We'll try to give you a broad overview of how programmers talk about things so that you can talk to your classmates and share your work with your peers.

Page 5 (the last page) is an "optional" page that you may not have time for. Feel free to come back to it at another time.

A programming language is just like any other language.

English is a language made up of words and syntax (think grammar, punctuation, etc.). The combination of using words and syntax allows for us to communicate with other people who speak English! But in English, there are situations where weirdness prevents us from understanding the meaning behind a sentence. Take, for example, the sentence: "I never said they stole my money." We might assume it means a particular thing, but if you said this sentence out loud...most people would interpret the meaning based on which word you placed emphasis (which we show in bold below) on:

I never said they stole my money. — Someone else said it. 

I never said they stole my money. — I didn't say it. 

I never said they stole my money. — I only implied it. 

I never said they stole my money. — I said someone did, not necessarily them. 

I never said they stole my money. — I considered it borrowed. 

I never said they stole my money. — Only that they stole money,  not necessarily my own. 

I never said they stole my money. — They stole something of mine, not my money. 

Computers can't deal (easily at least) with this ambiguity. So in a programming language, we limit ourselves to particular commands that are defined very specifically such that there is no ambiguity when you give the computer that command. Below, you'll interact with a microworld where you have the ability to ask the computer to run or process some commands.

Just like the value of a property might affect the outcome of a command, a parameter is a value that can be used as input to a program to change the way it behaves. Below we have our usual turtle sim, but with an important added feature, a slider at the top called NUMBER-OF-LAVA.

Use this new version of the model to answer the questions below.

When we construct sentences in English, we end up using quite a bit of syntax in order to make sure our meaning is communicated correctly. This often includes quite a bit of punctuation–seemingly meaningless symbols that drastically change the way we read/interpret a sentence. If you've ever seen a program in a traditional text-based programming language like Python, Java, or even something like Fortran, you're sure to have noticed the same types of things! Semicolons, indents, and parentheses are just some examples of syntax that are used in text-based programming languages to prevent ambiguities.

But today, we want to get programming right away and don't want to have to get used to using a text-based language. Instead, we're going to use a blocks-based language to program the movements of our turtle buddy! A blocks-based language is a computer programming language where programs are constructed visually, with commands "snapping" together just like pieces in a jig saw puzzle.

Below, we have our now familiar turtle simulator, but you'll notice a "Programming Canvas" to the right hand side. On the Canvas on the right-hand side you'll see the beginning of a procedure which tells our turtle how to MOVE. You'll see on the right-most side of your screen a set of 4 different blocks, three of which should remind you of the buttons we used to solve this simple puzzle just a few minutes ago.

While issuing commands one-at-a-time to our turtle was great, here we want to write our procedure using these blocks. In a way, we're basically programming the turtle's brain. We upload our program to its brain with the RUN PROGRAM button and let it do its thing. To add blocks to your TO MOVE procedure, just click and drag a block from the rightmost side of your screen and snap it, like a puzzle piece, on to the bottom of the TO MOVE block (use the little nibs on the blocks as a guide). Continue this process with whichever blocks you need to guide your turtle buddy to the safety of the violet patch. Once you've finished your program, use the RUN PROGRAM button to have the turtle run your program.

If your turtle hits the lava, it'll let you know and go back to its starting position. But if your turtle stays safe but doesn't make it to the goal, you'll need to change your program to accomdate its new position.

Note: If you try to stop your program while it is executing by clicking the RUN PROGRAM button, your turtle will likely get confused. If this happens to you, make sure to click the CLEAR TURTLE BRAIN button before trying again.

Now that you're experts, lets put your skills to some creative use. We have our delightful turtle buddy and some simple ways of controlling its movement. We also now know how to chain these movements (or commands) together into programs. But programs don't need to always be about completing some sort of task. What if we used our turtle buddy to create art? Computers are great at performing the same simple tasks repeatedly at amazing speed. Here, we're going to use a slightly modified version of our previous activity that focuses on drawing designs based off of your turtle buddy's movements.

There are a few main changes to this simulation:

1. We no longer have a checker-board grid. The patches are still there, they're just all the same color.

2. Your turtle buddy now has a pen with it and where it moves, the pen draws on the ground (you'll see what we mean). The color of the pen depends on the color of your turtle's shell.

3. The FORWARD, LEFT TURN, and RIGHT TURN command blocks are a little different than they were before. You'll notice each of them has now been parameterized. FORWARD now asks you how many steps that your turtle should step forward while LEFT TURN and RIGHT TURN ask you how many degrees to turn. Note that this is NOT the same thing as "changing the value of heading to right or left." Instead, it's turning at an angle. You'll see what we mean if you ask your turtle to LEFT TURN 90 degrees. If you were to ask it to LEFT TURN 90 four times....that's the same thing as LEFT TURNING 360...which is the same thing as not turning at all!

4. Oh, and we removed the lava...and the violet goal patch. Now you're free to draw to your heart's content!

5.  TO MOVE, has been replaced by TO DRAW. Unlike TO MOVE that only gets executed by your turtle buddy once, TO DRAW will be repeatedly executed by your turtle until you click the DRAW button once more to stop it.

You control the movement of your turtle just as before, by connecting movement blocks to each other and then, once satisfied, hitting the DRAW button (note: remember, once you've clicked the DRAW button, your turtle will keep following your program until you click DRAW again).

Use the simulation to answer the questions below. 

If you still have time, let's cover one more concept: conditionals.

A conditional is basically the computational equivalent of an "if - then" statement. For instance, if there's a chair beneath me, then I can take a seat. Conditionals are very powerful in programming because they allow us to perform different actions based on some condition.

Before, our amazing-turtle-saving-maze-program only applied to a single map at a time because we were just analyzing the situation ourselves and giving our turtle buddy explicit directions. What if our turtle buddy could do that sort of analysis by itself? Could we write an program that could solve any map?

Below you'll see our familiar turtle maze, complete with a Programming Canvas to the right with some additional blocks. The additional blocks are:

if patch-ahead: this block is a conditional that allows your turtle to check for one of four conditions. Is this patch ahead the goal? lava? safe? or an edge? This block will execute commands inside of it only if the condition is met.

maybe: this is a different type of conditional that depends on random chance. Your turtle will randomly choose to follow the commands inside of this block according to the probability you select.

randomly pick: this is yet another conditional that you might think of as an if-else statement. Your turtle will basically flip a coin. If heads, it will do the first thing. Otherwise, it will do the second thing.

Like our drawing turtle, your turtle will continuously run "to move" function you provide it until it meets an untimely doom or reaches the safety of the violet patch..

Using the provided blocks, try and come up with a to move program that can solve ANY of the mazes you throw at it. If your program successfully solves one puzzle, hit RESET and then run your program again.