Does Bad Code Lead to Good Learning?

Last week a teacher posted an interesting problem. They were looking for an explanation of why to code produced the answer that it did. The code is this:

    static void Main(string[] args)
     {
         int x = 2;
         while (x < 12 || (x % 3) != 0)
         {
             x += 3;
         }
         Console.WriteLine(x);
     }
}

The answer, which takes a while to appear, is 12. But why? It turns out that the value of x overflows. It overflows a lot! Eventually the combination of overflows results in a 12 appearing. It’s not at all obvious how this happens or even why this is not an infinite loop.

There was a lot of discussion of this in the AP CS A Teachers Facebook group. I did find it fascinating and wrote some debugging code to see what was going on.

I have to wonder about the value of showing this code to beginners. Or anyone really. What is the value of the learning, if indeed it does teach anything that beginners are ready to learn. Mostly it is not a great plan, in my opinion at least, to rely on number overflows. Different architectures, especially those with different work lengths, are going to take different numbers of iterations. Are they some that would never get to 12? I’m not sure and I don’t like relying on specific architectures.

BTW on my system with a full word this took 1,431,655,765 overflows. With a short it happens after 21,845 overflows. I still don’t know why it takes so many overflows but I am content for now.

In any case, is there value in asking students to figure out why 12 comes out?  I can see people disagreeing on its value as an exercise in debugging. I’m not a fan of it though for a couple of reasons. Firstly, why would you write that code? What is its value? Some people will find it to be an interesting puzzle for the sake of solving a puzzle. I did. But not everyone is “in to” such puzzles.  I think most people want to solve a problem to make something work and do something interesting.

I’m also not fond of code that is unclear as to its purpose and goal. In the Facebook group there were a lot of comments from experienced teachers who expected something completely different from the code. Infinite loops being the most common expectation. In fact, that this isn’t an infinite loop is highly unexpected. Code should be written so that someone can figure out what it does without actually executing the code. Especially for beginners.

Now I am not going to be critical of a teacher who does see value in this particular exercise but it’s not for me. As educators we often do create code just for the purpose of highlighting a specific language feature and small, not very useful pieces of code, often make up quiz/test questions for the sake of space and time. But for the most part I believe that students learn better with more context and with code that solves an interesting – to them – problem.

Related posts:

• Why Do I care About This Program I am Coding?
• Explain This Confusing Code

Scratching the Programming Itch

Programming is fun for me. It always has been.I’ve always written code to scratch a personal itch. That is to say that I like to write programs that interest me. If I can learn something new or try something different that is a plus. Not having a time pressure makes this even more enjoyable. I’ve written a couple of fun programs lately. I think they have some potential for student projects as well.

For example, my wife bought us some clothing from a company called Two Blind Brothers. It’s nice clothing and profits go to fight blindness according to the web site. The clothing all has labels in the braised bumps of Braille. Naturally one wants to know what the Braille says and while it is probably documented in the company web site I was looking it up letter by letter with a chart. Eventually I decided to write a program to help me out. Yes, programmers will spend an hour writing code to save themselves 5 minutes.

My program has a pattern of 6 dots that can be set or unset to match a Braille patter with the program displaying the appropriate letter. Or I can enter a letter and the program will display the pattern.

I’d love to assign this to students just to see the different ways students come up with to do the parsing and display. I’m probably going to use it as a platform for more experimentation. I have some other ideas about parsing and translating. It’s modular enough to make experimentation easier.

I’ve also been playing with a Yahtzee program. There are a lot of interesting facets to this program. One of them is verifying options. How do you recognize a full house? How do you recognize a straight? How do you make sure the values entered for a Chance or a three of a kind at legitimate? A couple of years ago I thought about using this as a project to use and enhance over the course of a semester. I ran out of time developing that but now that I have a program almost finished I may try to write up something like that.

Loops, arrays, classes (dice class anyone?) and more are all part of a project like this. It’s been fun writing it. I’ve learned a few things that may help me with some additional games.

Comments on Commenting Code

Comments sometimes seem to be a hot button for software developers. Opinions range from the manager I had who actually did want a comment on every line of code to the people who think comments are completely unnecessary. I tend to fall somewhere in the middle as I think most people are. We may draw the line differently but most people think there is a sweet spot for how many comments are a good idea.

Some people don’t see the value in comments. They believe that code should be self documenting. The variables and functions should have descriptive names for example. To some extent that is a valid goal. Code should be understandable by itself. That’s not always as easy as it seems. When we write code we do so with some specific, obvious to us at the time, information. This might not be the case for others who come to the code later. Or even to the original programmer after some time has passed.

When I talk to students about comments I often relate an experience of my own. I wrote a really cool (in my opinion) program while I was a university student. It drew pictures on a drum plotter. Pictures took about a half hour to draw on that device. Some years ago, decades after I wrote the original program, I decided to write the program again for a modern display device. I wrote the program, compiled it, and ran it. It didn’t look right at all. I stared at the screen and thought “that looks familiar. I think I made that mistake the first time.” Now it turns out that I still had the punch card deck (yeah, I’m that old) and could read through the original program. I came across a comment that read “this function takes degrees in radian” Ah, ha! That is what I got wrong both times. I simple fix and my program worked as I wanted.

Clearly writing comments, especially that one, paid off big time.

Something that took a while to figure out should always be commented in my opinion.

When ever the subject of comments come up someone brings up the case where code changes mean that comments do not match the code. There is no doubt that this happens but frankly I have no sympathy for the situation. A serious professional should be mindful of details like that in their code. When the code and comments do not match it means someone was in too much of a hurry to do a complete job.

Comments should document difficult things, non-obvious things (parameter lists to called methods are a good example, and anything that required some involved logic.

Student projects in a first programming course often don’t have the sort of complexity that a larger professional program might have so it is hard to get students to comment code. I always insisted on a complete header of comments at least. And a comment that describes the purpose of each method written. As I think on it today, I wish I had produced some larger piece of well commented code to have students read.

How do you feel about comments in code? And how do you communicate it to students? Please share some ideas in the comments.

Early Registration Open for the CSTA Annual Conference

Just registered for the 2021 CSTA Annual Conference Early discounted registration for CSTA+ members is now open https://web.cvent.com/event/354be991-0b98-48e0-b4d3-0e32b72a6e49/summary

If you are a CSTA+ member you should have the email.. If you’re not a CSTA+ member maybe you should think about becoming one!

I think its going to be a great conference. We learned a lot from last years conference on many levels.

Recursion–How and When to Teach

I’ll start with a confession. Recursion is one of those concepts that I struggled to understand in the beginning. Was it me or was it how it was taught? An open question that I don’t want to look for blame. A recent article by  Shriram Krishnamurthi, CS Professor at Brown University, called How Not to Teach Recursion suggests that maybe I was taught badly and worse still that I taught it badly.

Adam Michlin wrote an interesting, related, post called Why you shouldn’t teach recursion (yet)

The teaching of recursion is one of those topics that really gets people talking. I hope thinking as well. Certainly I have been thinking about it lately.

Teaching it early, teach it late (as Adam suggests), not teach it at all? All question people ask and answer differently.

My key takeaway is that recursion has to be the natural solution to a problem for it to really make sense to students. Navigating a tree structure, file directories for example. This implies a prior understanding of the related data structure is also required.

Some languages and teachers use recursion for iteration. I guess for some that feels natural but it never has for me. Perhaps I am to old school and too deep into for statements and while loops. When I started programming there were languages that didn’t support recursion at all!

I have had several students discover recursion (and stack overflows) by having the main function call itself. Very instructive.

I’ve been programming for about 48 years now and very seldom have I had a real need to use recursion. By need, I mean that was the bests and only way to code a solution. One time I wrote a really cool recursive method which I was writing code for a living. Upon code review the rest of the team made me rewrite it as an iterative method because they decided it was too complicated and no one else wanted to try to debug it some day. Most of the teach was fairly young and were recent graduates from top CS universities too!

How important is recursion really? The AP CS A exam tests it lightly in the multiple choice questions (as I understand it). The AP CS Principles didn’t test it at all. SO if you are basing decisions on those exams (which is a whole other problem IMHO) its not that important. Do an advanced data structures course on the other hand it is probably fairly important.

If you are teaching it though I think the important things are outlined in Shriram ‘s article. The popular examples are problematic at best. From the post:

Where does recursion come from? HTDP argues that it arises from self-references in data. That is, recursive data suggest recursive solutions. This is the key insight you need for understanding recursion. Not only does it make sense once you think about it, it also demonstrates why most other approaches to teaching recursion are essentially incorrect.

But do read Shriram’s article. He explains it much better than I can.

[Edit: Mike Zamansky gives some thoughts on teaching recursion at On Teaching Recursion
Worth the read. ]

[Edit: Michele Lombardi gives here thoughts at Chiming in on Recursion

Looking Forward to 2021 in CS Education

What a strange year it has been. The pandemic and more took a lot of the steam out of what I had hoped to dig deeply into in 2020. Surviving is success in these times I guess. I taught online for the winter/spring semester of 2020 and then retired. Teaching online was not so bad but it didn’t leave me with much time to improve on things. Running as fast as possible to stay in the same place seems to have been the norm for most teachers.

But this is time to look forward not back. One thing that seems to have grown among the teachers I see on social media is cybersecurity. While we have seen cyber security at the CSTA conference the last several years is feels like 2020 was the year teachers started teaching it in larger numbers. I think that is only going to continue.

I see a lot of teachers looking for new courses that are relevant to students and cybersecurity certainly counts as that. We can also fit more of it into other CS courses. Students love it. Well, mostly.

CYBER.ORG (formerly NICERC) is one of several organizations supplying curriculum and professional development. And it is all free.I love that team.  Teach Cyber  is  another group as is TryHackMe There is a pretty active Cybersecurity Educators group on Facebook where a lot of teachers are sharing ideas and resources. I highly recommend that group.

Other than cybersecurity what am I looking to see more of in 2021? Well, online IDEs which really came into their own in 2020 are going to only get better. We’ll probably see more competition there as well. In fact, any option for teaching online will see growth even if, as we all hope, schools all return to in-person learning. Giving access to students outside of computer labs is just too powerful a tool to avoid.

I expect computer science, indeed most, conferences to retain a virtual component in 2021. Will they be mixed with both in-person and virtual aspects? I’m not sure but I see more and more conferences having the ability for people to attend virtually. The cost of that is coming down for the conferences and the ability of teachers to spend money for airfare and hotels is not growing as fast as the need for more teachers. There is also a growing interest in reducing carbon footprints on that part of many people.

Computer science education research has been gaining traction in universities. That’s pretty exciting to me as I think there is still a lot we can learn about how to teach CS more effectively. I am hoping that learning about the results of this research will be more available to teachers as well. We can’t all go to conferences or afford expensive peer reviewed journals. The real value of CS Ed research is getting the knowledge to actual teachers.

I see reason to be optimistic about CS education in 2021. We made it through 2020 and it is all going to get better. I can’t wait to see what happens!

Looking Back on Computer Science Education in 2020

What a year it has been. I was reading my start of the year post from January. The closing was “2019 has some serious potential.” I had no idea what was to come in 2020. By the middle of March I was teaching online to students who were doing their best to learn from home. It really changes a lot for teachers and students.

So what changed? Well, there was some serious growth in online development tools. Teachers moved to or increased their usage of tools like GitHub, Repl.it, and other online IDEs.  I still like the solution my school used (and continues to use now that they are mostly in-person) of a cloud based virtual machine. That the big cloud companies (I’m looking at you Microsoft and AWS)  haven’t jumped on this means they have missed a huge opportunity in my opinion.

Plans for a lot of physical computing went by the wayside as schools either didn’t have equipment to send home with students or didn’t want students sharing devices that could not be easily sterilized. I suspect emulators got a lot of use.

Along with school, conferences went virtual in 2020. It looks like that will continue into 2021 as SIGCSE will be virtual. It’s still uncertain if CSTA 2021 will be virtual or in-person.  CSTA 2020 went pretty well online. I enjoyed presenting virtually. Though to be honest it wasn’t quite as much fun as presenting in-person. I couldn’t hear people laugh at my jokes for one thing.

For myself, the biggest change of the year was retiring from the classroom at the end of June.  So I have missed most of the crazy on the fall of 2020 school year. I have been watching what my friends have been going through though. I guess I picked a good time to retire. I do miss the kids though.

Pythagorean Theorem Day Programming Project

I’ve been doing little programming projects for my own amusement. I thought about doing Advent of Code like the cool kids are (Looking at you Mike Zamansky who among others is blogging about those challenges) but I just can’t get into them. I need to scratch my own itch as it were. The other day a friend posted on Facebook that the date was a Pythagorean Theorem Day – 12-16-20 because a right triangle with a height of 12, a width of 16 has a hypotenuse of exactly 20. It’s a cute idea if we ignore that the year is really 2020 not just 20.

I commented that calculating the next Pythagorean Theorem Day would be a fun little programming project. Today I thought I would try it myself. The set up is pretty easy. Nested loops for month and day and using the usual math.

There are two issues. One is that not all months have the same number of days. The other is that we want an exact whole number for the hypotenuse.  The first was solved by creating an integer array with the number of days in each month and using those values in my equation.

The second took some thought. There are probably some really cool mathematical ways to do this. I thought about this and decided to cheat a bit. I converted my floating point result into a string, cast it into an integer, converted the integer value to a string, and then did a string compare. The result of the compare determined if I displayed the result or not. There are 12 such dates in case you are interested. Only two of them are after 20 though.

I leave figuring the rest out as an exercise to the interested (or assigned) programmer.

A few things make this a nice student project in my opinion. Nested loops of course, using an array to simplify the programming, and what ever you use to determine if the hypotenuse result is an integer or not. And it is short so you can use it as a demo or an in-class project.

What do you think? How else would you determine if the result was an integer or not?

Musings on the Goals of High School Computer Science Education

Recent conversations on Twitter and Facebook have had me thinking about the goals of teaching computer science in high school. There is no single goal and it probably varies some by teacher, school, and student population. My goals were basically:

• Give students a basic understanding of computing and computer science to better understand the world around them
• Create an interest in computer science so students are willing to learn more.
• Create in students the idea that they can “do computer science.”

I would rather not prioritize them. I think I did a pretty good job with the first goal. That’s probably the easy one though. But it is pretty important. Helping students better understand the world around them is at the heart of a lot of education. We don’t expect every student to be a novelist, a biologist, a chemist or a professional mathematician. So we are not (usually) expecting HS CS students to become professional programmers.

The second listed goal is pretty hard to measure objectively. I hope I made my classes interesting and the subject itself interesting. A number of students did go one to major or minor in CS so there is that. I hope I didn’t turn too many off.

The last listed goal is also hard to judge objectively but it’s really important. People don’t continue to invest time if they don’t thing they can succeed. Any one can learn computer science. Anyone can learn to program. Some may have to work harder at it than others and some will find it more interesting than others. Student have to know that they can do it if they choose to try.

If students choose to study more CS I want them to have a solid base to build on. I think that is a given. Right? Unless I succeed at the three listed goals above there is not much point in anything else though. So I made the course rigorous and I try to teach the concepts and ideas and good habits that I learned over the decades. I do it with a goal of building success, interest, and understanding of computers in the world today. I’m not just trying to teach the computer science nerds, no matter how much I love then, but all of the students in my class.

Dreidel Game–A Chanukah Programming Project

If you’re anything like me, you like to assign projects that have some relationship to what is going on in the world. Holidays are one such thing. December brings the Jewish holiday of Chanukah – usually right before Christmas. The Dreidel game is a game traditionally played during the Chanukah celebration. It is played with a top that has four flat sides. Each side has a letter of the Hebrew alphabet.

ש Shin ה Hey ג Gimmel נ Nun

The game has multiple players each of whom is given the same number of tokens. Players all place one token in to a “pot” and spin the dreidel to see who goes first. The player who spins the highest value starts. Note: nun is highest, then gimmel, hey, and shin. If there is a tie, the players who tied spin again.

Each player takes turn spinning the dreidel and taking an action depending on what letter they spin.

* Shin: put one more token in the pot
* Nun: do nothing
* Gimmel: take all tokens from the pot
* Hay: take half of all tokens lying in the pot.In case of an odd number of tokens, round up.

The game ends when one player has all the tokens or after some set period of time or mutual agreement.

There are lots of ways to program this of course. Normally, at this point in the semester I have been teaching students how to create simple classes. So when I wrote my solution I created a dreidel class. There are some reasons that this makes for a nice class to create. There is the usual protected data – the face value of the dreidel. And there is the obvious spin and get value methods. I also over loaded the ToString and CompareTo methods.

The ToString method allows for displaying the name of the face value of the dreidel. CompareTo is particularly useful for selecting the high spin at the beginning of the game.

I also added some public const values for the face values so that I could use them in calling programs without the programmer needing to know what the actual values are.

if (player.Value== Dreidel.Shin)

Here we have a fairly simple game to program with a class that lets the programmer do some interesting overloads and activities without too much complexity.

Inspired by a project idea posted on the AP CS Teachers Facebook group group (https://www.facebook.com/groups/APComputerSciencePrinciples/permalink/1873272652824371/)  Thanks to Lee Whiteley for sharing with the community..

New Resources for Teaching and Learning about Artificial Intelligence

Earlier this week I was a guest speaker in a computer science class (via Zoom of course). It was fun to be back into a class and interacting with students. The students were asked to prepare questions for me and many of the questions were about artificial intelligence. That’s not surprising as AI has really jumped into the public in ways it hasn’t before. That’s why it is timely that code.org has created a new resource for teaching and learning about AI.

The main resource page for this is at https://code.org/ai There you will find a bunch of short videos of 3 to 5 minutes that cover various aspects of AI. Several of the videos explicitly focus on getting people to think about the ethics involved. Satya Nadal, Microsoft CEO, in his introduction makes one of my favorite points right off the bat. It is not enough to think about what computers can do but we also need to think about what computers SHOULD do. Ethics are woven into all the videos and not just the once focusing on ethics.

The videos are typical code.org videos. That means high production values and a diversity of impressive speakers. Presenters represent a variety of ages, races, and colors. They are all impressive and are practitioners in the fields of AI. There are academics and there are people from industry. They really highlight a broad cross section of people involved in AI today.

Besides the code.org videos there are links to videos from other organizations, lesson plans, and activities powered by artificial intelligence and machine learning. And more. It’s a great place to start building the set of curriculum that will work for your course and the age group you teach.

Why Do I care About This Program I am Coding?

Why do we program? Well, for some of us it is because we get paid to write code. For some it is part of our learning experiences. For a few it is the fun of it. There are a lot of motivations and they are different for different people. A couple of posts have been thinking about this lately.

Mike Zamansky has bee posting about the Advent of Code event. (Mike’s initial post here Advent of Code 2020)  Today I replied to his post about the first puzzle with the following.

I struggle with these problems a bit. Not because of the technical issues but because of motivation. Or perhaps relevance.  Why would I need to do this? What interesting or important problem does it solve? I guess the issue for me is that solving a problem for the sake of solving a problem, proving that I can did it basically, is not motivating to me. Maybe I have been programming too long to feel like I need to prove anything to myself. OR anyone else for that matter. I get that for some the challenge is enough motivation and that they get satisfaction from the effort. The journey being more important than the destination I guess. And that is fine and if people enjoy doing it that is wonderful. I'm happy for them. It just doesn't motivate me.

As I thought about it, this also related to a post by Mark Guzdial recently. Purpose-first programming: A programming learning approach for learners who care most about what code achieves: Katie Cunningham’s Defense I hope to be able to hear Katie’s defense tomorrow. And look up her papers.

When we as educators assign projects or do demos, what is the purpose of of the code? And does anyone care about it? Students work harder and longer, it seems to me, on projects that they care about. Not just for the grade though that motivates some. Do they want to see the program work for themselves? I always found that the hardest working most motivating projects were the ones students selected or decided upon on their own. Projects that solve problems that are meaningful for them are much more effective than projects that are more about “just do this to learn how this concept works.

I’ve been playing with code myself lately. Each project has taught me something but I was motivated more to solve a problems that was interesting to me than to learn the new concept/algorithm/language feature or what ever I learned. This is what we as educators need to bring to our students in my opinion. They have to care about the problem and not just the grade.

Does It Matter How Fast the Code Is?

I’ve been having a lot of fun playing with code lately. One of the things I have been experimenting with is cryptography (See Tiny Book of Simple Cryptography) For one project I wanted to create a string of ones and zeros to represent the binary value of letters. I quickly came up with three ways of doing this. I know that are probably many more ways than that. But for now I have some that work and one of them I really like.

Which one is best? Well, that depends. Which one is the fastest? That depends as well. I think I know which one is fastest. It uses the bitwise & operation which generally is pretty quick. One used the Math.Pow function which I suspect slows things down quite a bit. The third uses nothing fancy at all and could easily be coded by someone with only a little programming knowledge. I suspect it is the middle in speed/ Does the speed matter though?

In this application , probably not. The bottleneck in performance is going to be in the I/O not the calculations. The performance of this function is lost in the noise.

What probably matters more, if one is looking to define “best”, is which algorithm is easier to understand..

I learned this lesson one day back when I was writing code for a living. We were doing a formal code review of my code and I had written what I thought was a very clever piece of code that was pretty efficient. The review made me rewrite it using code that was no where near as clever or interesting. It was, however, a lot easier for someone new to the code to understand. And that was more important.

Now there are applications where performance is critical. I remember working with a company building a system  to collect weather data. They collected a huge amount of data is a very short period of time. They were actually comparing the instruction execution times of various machine language instructions to pick the computer they were going to buy. That’s pretty exceptional though.

To complicate matters even more, today’s optimizing compilers are very smart. It is rare that a person coded Assembly language program can outperform code generated by an optimizing compiler. I was involved in actual benchmarks of this in the 1980s and things are improved since then. Take these two pieces of code:

if (foo % 2 == 1)

label1.Text = "Odd";

if ((foo & 1)==1)

label2.Text = "Odd";

Which one is faster? You may think the second one is faster. You might be right. On the other hand, a really smart compiler by generate the same low-level code from both of them. Unless you were on the compiler writing team you probably don’t know. Even if you have the source code for the compiler do you really want to spend the time to see how it is optimized?  You couple probably also look at the generated code but is that worth it either? Not generally.

The first example is clearer. A number of my friends who write code for a living tell me that is what they would use. Because it is clearer and understandable by more people it is not worth worrying about an optimization that may already be taken care of for them by the compiler.

Once upon a time it mattered a great deal if one iterated though a two dimensional array by column first or by row first.  One had to know which was faster and do it right. Today, compilers take most of the worry about this away from us. We can do it in the way that seems more logical for us and for the application.

One of my friends who has worked on compiler development teams tells me that conversations about this sort of optimization are frequent there. People working on compilers have the time and the experience to make compilers smart. I’m pretty sure more of them (the people and the compilers) are smarter about code optimization than I am.

That doesn’t mean we can ignore performance. I’ve seen some beginner code that is horrible in performance. But still there are trade offs. I once wrote a very slow program that I ran once a month. I thought about a way to optimize it that would cut a minute or two off of the run time. It would have taken me an hour to code and that was a lot more time than it would have saved me. Turns out a faster computer a few months later ran the inefficient code a lot faster anyway.

Honestly, though discussion optimization and performance can be fun for a certain class of geek. Geeks like me.

The Making of a Computer Science Teacher

There is quite the conversation going on in the private Computer Science Educators group on Facebook about teacher preparation for CS educators. This is a very interesting group for CS educators BTW. Join if you are on Facebook. I link to some specific articles at the end.

It’s a lot more complicated question than it might appear. There is the argument about what CS educators need to know to teach CS effectively. Is something better than nothing or is not enough going to mean poorly prepared students? Given all the complaints I have heard from university people about high school students being taught CS wrong (what ever that means) I tend to believe that CS educators should have a lot more depth of knowledge than the courses they are teaching. Definitely more depth than their students will get from the course. We expect this from teachers of other subjects (for the most part – see highly qualified teacher).

As to preparation, and its close cousin – certification – we are dealing wtih three main types of people who need preparation to teach CS.

• Teachers of other subjects
• CS experienced people moving into teaching
• Career beginners who are not previously teachers or CS people

They all need something different. I have heard people say that a good teacher can teach any subject after learning some content knowledge. I would argue that teaching CS is different from teaching most other subjects. A teacher needs to know how to teach computer science. We've been fortunate over the last decade or two that some serious research in how to teach CS has been done. CS teachers need to know what has been learned about HOW to teach.

Teachers of other subjects also need some solid content knowledge. Topping out at the content involved in AP CS Principles and AP CS A (the top high school cs courses) is not enough. Well, not for high school CS teachers. Students are going to ask deeper questions than what is required and you can only get by with “well, let’s look that up” so often before people start to wonder if you know what you are doing.

How much do you need? And this goes for people new to teaching as well as just new to teaching CS. That’s a struggle. I don’t think you can get it in two one semester courses let alone a couple of weeks worth of summer workshops. Two semesters of programming is probably the minimum for that aspect. In the first one a person learns a programming language and a start of how to solve problems. It takes a second course to really become a programmer. Of course there is a lot more to computer science than programming. Vocabulary, networking, algorithms, security, CS ethics, and well, if your have taught AP CS Principles you get the rest. So three or four semesters of real CS.

Everyone who teaches CS including those new to teaching and those career changes needs a course or two (or three) if pedagogy. A focus on teaching CS for sure but also some work on test development and evaluation and classroom management. Do they teach classroom management in regular education programs? CS has some interesting complications involving students playing on the internet and messing with lab computers.

I also think that CS teachers, especially now when there are seldom multiple CS teachers in a building, need to learn about external resources. Social media, CSTA, summer workshops and conferences, StackOverflow, and generally how to build a network to support your growth as a CS teacher.

To prepare to be a great CS teacher is going to take a lot of work. Yes, people do figure it out on their own I know people, I am one, who came to industry without training in teaching and did a pretty good job. Enthusiasm and great students will get you pretty far. That’s not the ideal I look back and wonder how much better my students would have been if I had known what I know about teaching CS back then. I don’t think I messed anyone up too much but could I have taken them further? I like to think so.

If CS is going to take its place with other core subjects we have to learn to teach it well. We have to have more than just enthusiasm for the subject.. We have to set high standards for teachers as well as students.

Facebook Conversations

• https://www.facebook.com/groups/cptrscied/permalink/886841201720689/
• https://www.facebook.com/groups/cptrscied/permalink/886035605134582/

Mike Zamansky’s post of the subject https://cestlaz.github.io/post/teachers-can-learn-cs/

Tiny Book of Simple Cryptography

I've been playing with simple cryptography. Mostly stuff that was solid before computers. Just for fun mostly but some of it may make for interesting projects for students. I've written a little bit about the things I have been playing with.

This is not a big book and it is intended more to spark interest and not to be a real reference book. There are footnotes linking to Wikipedia articles that would be a good next step for learning more.

I have a couple of substitution ciphers and a couple of  transposition ciphers. Added some Steganography. 

http://www.acthompson.net/TinyCrypto.pdf

Comments and gentle criticism welcome. I have coded solutions in C# that are ok. Some of them even have comments.

Updated 5 March 2021 to include a brief chapter on the PigPen Cipher. Also some minor edits in other sections.

TileCode–Creating games on and for handheld devices

People are Microsoft always seem to be working on interesting and unexpected (to me anyway) things.  My most recent discovery is TileCode. From the website:

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Microsoft TileCode is an app for designing, coding, and playing video games directly on low-cost MakeCode Arcade gaming handhelds, as well as in the web browser. With TileCode, we are using the medium of video games to explore the combination of

• Natural language for informally specifying games goals, rules, and mechanics;
• Physical computational models that foreground concepts such as data parallelism, pattern matching, and conflict resolution;
• Testing and debugging of programs to establish confidence in their behavior and to refine specifications;
• Machine learning to help bridge the gap between natural language and programs, as well as to generate non-player character behavior in games.

Our ultimate goal is to provide a sandbox in which students can express and refine their game ideas, while learning about computation, programming, and machine learning, supported by software engineering practices.

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It's a pretty interesting idea. I wonder how it might work in classrooms. There is a webinar about their research later in November that I hope to sit in on.

TileCode builds on a lot of previous work and not just from Microsoft. It builds on Kodu and MakeCode but they reference a lot of other block based tools in their paper - TileCode: Creation of Video Games on Gaming Handhelds

I'm really fascinated by the work I am seeing in domain specific tools lately. While games are a popular topic I'm been following Mark Guzdial's work with domain specific languages for Social Studies with interest. I tend to think that rather than see artificial intelligence take over the job of programming that we’ll see more and more domain specific languages (should we call them tools?) that people will use.  I’m not convinced that AI and machine learning will know when rules are really guidelines.

What If We Asked Students To Write Textbooks?

A professor friend on Facebook posted that a student emailed him to say that they textbook the were using was “crap.” I suggested in jest that he asked the student to write a better one. That’s pretty tough since how do you write a textbook about something you are learning as you go? (Can be done. Is painful. Don’t ask how I know this.)

The exchange got me thinking though. Supposed we asked students to write a chapter for a mock textbook? Or perhaps asked them to write step by step instructions for completing an exercise assignment. After it was covered in class but perhaps in lieu of a test.

I think it would be interesting to see how students explain concepts. Have they write to explain things to people their own age. How would they explain things? What words would they use? What examples would they give?

They say that to really understand something you have to be able to explain it to others. 

Somehow I don’t think most students would like this exercise though. Of course we already ask students to do things they don’t like – taking tests being one of them.  I do think that it would give us insights into what they do understand and how they understand it. Or misunderstand it as the case maybe.

Anyone want to try it?

Thinking About the Algorithms in Our Lives

My wife and I use these fitness trackers, ours are made by Garmin, to keep track of our activity during the day. Each day the devices give us a goal for how many steps we should take that day.  The goal goes up or down depending on how many steps we did on the previous day. I think. Maybe.

Being the computer guy that I am I keep thinking about how the algorithm actually works. Is it a simple algorithm based on some sort of average or does it have some amount of smarts? Does it take several days activity into account or just the previous days? Like so many things in our lives the algorithm is completely opaque to users.

Google Page Rank, the algorithms that run on the computers controlling our cars, and the software John Deere uses to control the equipment they make. (see article linked below for way this opacity is a problem for some) are all secret. Why?

Well, various companies have various reasons for keeping their algorithms secret. Competitive advantage is the reason for some. For many it is to keep people from “gaming the system.” Google, and other search engines, don’t want people to find ways to get unfairly high placement in searches. I suspect some of that is involved in my Garmin’s secrecy. For others, it is about keeping control of the how the systems them make are run – often for the sake of safety. That’s why many companies don’t want their software “messed with.”

How good or bad this is for the consumer is quite up for debate. There are solid arguments on both side. Arguably, the right thing depends on the situation in many (perhaps most) cases. These are issues we need to think about going forward. People who write software and create algorithms have a responsibility to make the right decisions about secrecy or openness. The decisions have to be about more than just money as well.

Do you discuss these issues with students? I think we need to do so.

Farmers Fight John Deere Over Who Gets to Fix an $800,000 Tractor

Artificial Intelligence, Humor, and Appreciation of Beauty

Last night I started re-reading Heinlein’s The Moon Is A Harsh Mistress.  It’s an old book, written in the mid 1960s, so there are some old ideas about computers and computing in it for sure. There is some hand waving about how AI is done and how the computer, Mike or Mycroft Holmes, becomes self aware. It is fiction after all. The computer is trying to understand humor and a human friend is trying to help. One way he is helping is to get lists of jokes and report back on which jokes are funny, which are funny once, and which ones are always funny. That sounds a bit like machine learning we see today I think.

In any case, even is the computer does understand humor at some level and is able to create jokes that people find funny does that mean it has a real sense of humor? Will it be able to laugh at jokes that are not in its system? I wonder.

This makes me wonder about other things. We know that AI has been able to write music that people enjoy and create art that looks like it was done by master artists. Is creating art or music the same as enjoying art and music? Maybe not. Now human artists “hear” music in their heads before they write it down or play it. Beethoven write music while he was deaf and so could not hear it being played.

I’ve been to a number of wine tastings. I don’t like wine. No matter how many times I taste it I just don’t enjoy the taste. Listening to wine experts talk about wine and tasting it myself I think (could be wrong) I could learn to identify the wines that wine lovers like. I don’t see me enjoying the process very much though. Understanding is not the same as enjoying. Is it the same for computers and AI? I think so.Recognizing beauty or humor or music is not the same as enjoying it.

The difference between humans and AI is that humans enjoy their creations. And they enjoy the creations of others. If we think about creating beauty as enough to  being human-like  I think we have a narrow view of humans. What do you think?

MicroBlocks For IoT and other Physical Computing

Well, there is a new tool in town for programming micro devices like the Micro:bit and the AdaFruit Circuit Playground Express and many more! It's called MicroBlocks and was created by a rock star team with experience with creation of such tools as Scratch and Snap!. It’s pretty exciting for a number of reasons. One of them is the wide variety of devices it works with. Another is the Natural Languages it supports.

Live Coding is another interesting feature.

MicroBlocks is a live environment. Click on a block and it runs immediately, right on the board. Try out commands. See and graph sensor values in real time. No more waiting for code to compile and download.

And Multi Tasking.

Want to display an animation while controlling a motor? No problem! MicroBlocks lets you write separate scripts for each task and run them at the same time. Your code is simpler to write and easier to understand

I played with it a bit and it looks pretty intuitive especially for those with previous block programming experience. I made the mistake of trying it without having a device to use with it handy. I have several at home and so I’ll be trying them next week. But I wanted to get the word out so that if people want to try it over the weekend (yeah, I know you don’t have as much free time as you want) or have some students try it out you could.

Sometime next week I want to do a side by side comparison with MakeCode which supports several of the same devices. Some obvious differences are that MicroBlocks supports running the exact same app on different types of devices and that MakeCode has emulators. Since most people only use one type at a time and have physical devices the impact of those differences will be different in different environments.

We are living in exciting times!