In Chapter 1, I gave you some examples of real-world programs. Would the following example have made any sense?

How can you read page 55 if you haven't yet been told which book to open? You might answer, "Yes, but I'm in math class, and the teacher said turn to page 55. So I'm sure the teacher means my math book!"

That's true. As a human, you are able to figure out certain instructions on your own. But remember—robots aren't that smart! They need to be given very strict and specific instructions. And those instructions need to be given in a specific order. That order is another way of saying "program structure."

Think of a house. You can't have a second floor without a first floor to build on top of, right? And you can't install a roof before you pour the concrete floor and build some walls. There's an order to how things are done when you build a house. The same goes for programming a robot.

Let's get out SPOT for another example. He's still doing his one and only trick—sit. You're not quite ready to upload an NXT-G program yet, but let's do some preplanning at this stage. I want you to use something that computer programmers call pseudo-code. What is pseudo-code? Well, the definition of "pseudo" is fake (as in pretend, simulated, virtual—get the idea?); it's not real. And "code" is simply another word for program. Put it all together and one way of looking at pseudo-code is this: fake program.

Our fake program isn't going to be written using NXT-G. The best way I can tell you to start creating a fake program is to pretend that SPOT has ears and tell SPOT what you want him to do. Let's try writing some pseudo-code using a numbered list:

That's pseudo-code? Well, it's a form of pseudo-code. Remember how I told you there are different programming languages? People write pseudo-code differently, too. The point I want you to understand is that before you can really program your robot using NXT-G, you need to have an idea of exactly what your robot will be doing. The easiest way to do this is to simply write down, in simple language, instructions for your robot. That's the beginning of a good structure for the future NXT-G program.

When you write pseudo-code, you are accomplishing three things:

You will use this pseudo-code to assist you when you begin to create your program with NXT-G. One final thing I want to mention about pseudo-code is that each instruction you give the robot should be as simple as possible. Take a look at the next two examples and tell me which one has the simpler instructions:

Which example is less complicated to read? If you said Example 2, you are right. Let's be honest—some humans would be confused if you gave them the instructions in Example 1! When writing pseudo-code, break down your instructions into short and simple statements for your robot. This will make it easier for you to convert your pseudo-code to an actual NXT-G program.

Are you wondering how you convert pseudo-code to a real NXT-G program? Let me give you a small preview of what's to come in the chapters ahead.

Take a look back at my original pseudo-code for SPOT and read step 4, "Now move backward until your Light sensor detects something black. Then, stop."

If I am programming in NXT-G and am familiar with all the tools it contains, I would realize that there are tools (called blocks) that match up to my pseudo-code. Why are they called blocks? Take a look at Figure 2-1.

Figure 2-1. A collection of NXT-G blocks that make up a program

See those three squares located in the center of the NXT-G software screen in Figure 2-1? Those are blocks! The block on the left (with gears) is the MOVE block. The block in the middle (with the little speaker icon) is the SOUND block. And the block on the right is the SENSOR block—its icon tells me that it's the Light sensor block. Don't worry, you'll learn about all these blocks and more in future chapters (the SOUND block is covered in Chapter 6 and the sensors are covered in Chapter 9), but for now I just wanted you to understand what a block is and what it looks like.

When I want SPOT to move backward, he's going to use his motors, right? Well, I'll be using something called a MOVE block. The MOVE block will allow me to program my robot to spin the motors (and wheels) in reverse, so SPOT moves backward.

I only want SPOT to back up until his Light sensor detects the color black. To do this, I'll use something called a SENSOR block to monitor the Light sensor. The SENSOR block will be programmed to look for the color black.

Finally, I want SPOT to stop when the SENSOR block detects the color black. For this, I can use another MOVE block that tells the motors to stop spinning.

You will use these blocks and many more to properly program your robot to follow your instructions. This book will teach you about all the different NXT-G blocks, so you'll know which ones to use when converting your pseudo-code to an NXT-G program.

If you can remember one thing from this chapter, it should be this: Programming your robot will be much easier if you take the time to write down the pseudo-code. If it helps, pretend your robot has ears, and tell it what you want it to do. Write down these instructions, and keep them short and simple.

Now, I want to give you some practice in writing pseudo code. It won't take long, but it will require a partner. Ask a friend or teacher or parent to help you with the following two exercises. (Possible solutions to the exercises in the book can be found at the end of each chapter.) If possible, switch roles with your partner for both exercises. This will help you write pseudo code as well as see how easy (or hard) it is to follow instructions.

In the next chapter, you're going to write some pseudo-code and actually convert it to an NXT-G program. The key to writing excellent NXT-G programs is understanding how the NXT-G programming blocks work. When you know how the blocks work, you'll know which blocks to use when converting your pseudo-code.

Chapter 3 is going to demonstrate the DISPLAY block, a very useful block that gives your robot the ability to write things to its LCD screen for others to read.

There is no single hard-and-fast solution to each of the exercises in this chapter. Many solutions are possible. I present two such possible solutions here. Your own solutions may be different in some details, but overall they should be similar to the ones presented here.