6 ms·

How We Teach Introductory Computer Science Is Wrong

78 points by nreece 17y ago

tokenadult 17y ago
Aren't there some good books that show an overview of what programming is all about? For example, those at http://olympiads.win.tue.nl/ioi/study/books.html http://olympiads.win.tue.nl/ioi/study/books.html include a few quite accessible books (and several more that are very hard). How about guidance into C via The Art and Science of C: A Library Based Introduction to Computer Science by Eric S. Roberts http://www.amazon.com/Art-Science-Library-Introduction-Computer/dp/0201543222/ http://www.amazon.com/Art-Science-Library-Introduction-Compu... or guidance into LISP with the famous Structure and Interpretation of Computer Programs (SICP) textbook? http://www.amazon.com/Structure-Interpretation-Computer-Programs-Engineering/dp/0262011530/ http://www.amazon.com/Structure-Interpretation-Computer-Prog...
jacoblyles 17y ago
A human teacher isn't always available to demonstrate things. How can we duplicate the experience of teaching for people with nothing but a browser and desire?
wooster 17y ago
I learned to program by reading code others had written. This was way before college. By the time I got to college, I had years of experience reading Perl scripts and very complex C networking programs. If there's one thing I would fix in CS curricula, it would be to make students read more code. When I was at Apple, I wrote a lot of software to make it easier for Apple employees to read code that other people in the company had written. That software has since been called "the most important thing to happen to software engineering at Apple, ever" by someone who is very high up in the org. chart. I have written a lot of code, and that has made me a good programmer. Reading a lot of code, however, has been even more important.
- pmjordan 17y ago
  When I was at Apple, I wrote a lot of software to make it easier for Apple employees to read code that other people in the company had written. This idea of improving the reading/understanding experience with software is something I've tinkered with, without much success, so your story intrigues me. If you can say & don't mind, what sort of approach does/did that software take?
- mechanical_fish 17y ago
  It makes sense. Writing prose works the same way. Learning to write is all about reading. One thing I've noticed is that I like to reread. I get through a lot fewer classic books than many of my obsessive-reader friends because I take time to revisit books over and over. And it occurs to me that this, too, is a key activity in writing: One must read sentences and paragraphs again and again to refine them.
10ren 17y ago
Re: examples vs problem-solving: I found that attempting a problem that was beyond me would prime my mind, so that when I read the solution, my mind would grab it. Like an enzyme. Apart from focusing on the relevant aspect of the material, it also provides motivation, and then satisfaction though tension and release. Something of a drama/sales technique. [EDIT it also combats that feeling of not having learnt anything in 3 years, by giving contrasting experiences of not-knowing and knowing. All humans are intelligent; I believe learning is just a matter of paying attention, which requires motivation and confidence. A sense of progress helps both.] I tried this on a class when I was tutoring at uni, and it seemed to work well. Students were surprisingly interested in the answers to puzzles I put on the board at the start of each tute, even though I didn't refer to them, and several did extremely well in the subject. Unfortunately, I have no comparative data with other tutes, due to "privacy issues", which averages would have overcome. So much for my dept's interest in teaching quality.
fnid2 17y ago
Extreme programming could be a better alternative. Have the experienced person solve the problem while the novice types out the solution. It's better than simply reading the solution, because you're hearing the rationale for the lines as they are being written. Writing them burns them into your brain. Perhaps we can group sophomores with freshmen. The sophomores are tasked with solving the problems and the freshmen are tasked with typing out the code. It also primes the seemingly naturally introverted programmers for group based activity that will benefit them in the long run.
- swolchok 17y ago
  Perhaps we can group sophomores with freshmen. The sophomores are tasked with solving the problems and the freshmen are tasked with typing out the code. It also primes the seemingly naturally introverted programmers for group based activity that will benefit them in the long run. I think this is an awful idea because the average freshman will learn from the output of the average sophomore, which is not good at all.
  - techiferous 17y ago
    This is a technique that teachers use and it can be effective if done right. Of course you have to make sure the "sophomores" know what they are doing. It works for a variety of reasons, including more one-on-one time and the fact that you learn best what you teach (yes, the sophomores will be learning, too).
- samdk 17y ago
  At least in my case, this wouldn't have worked at all. Most of the stuff I wrote as a sophomore was orders of magnitude more complicated than what I was doing as a freshman. I wouldn't have understood what was happening at all.
  - fnid2 17y ago
    That's okay. It'll be that way forever. I look at code I wrote 6 mos ago and gasp at the inefficiencies. If the freshman finds a better way, all the better -- the sophomore learns more too!
techiferous 17y ago
This reminds me of some teacher training I received a few years ago. The teacher was showing us a technique for teaching a new skill to people: * First I do it. (Step one is blah, then we do foo, etc.) * Then you help me do it. (So what's the first step? and then what do I do? etc.) * Then I help you do it. * Then you do it. The first part is important: new learners simply watching an experienced teacher applying the skill.
- mbrubeck 17y ago
  My best CS professors would write code on-screen during lectures (usually in a REPL, or sometimes an IDE). The great thing about watching them coding "live" is that you can see into their thought processes: which mistakes they make, how they figure out the mistakes and recover from them, exploratory code they write and throw away, the order they do things, how they evolve simple examples into complex programs. You don't get any of that from just seeing the finished product. It's also great for picking up mundane practical tips, like tab completion, GNU screen, shell history, and how to quickly look up documentation.
  - branden 17y ago
    Yes, yes, yes. My favorite programming instructor would often code in front of the class on a projector. Like you I learned a bunch of little tricks, and it also built confidence. If he can write an AVL tree in front of my eyes in an hour then man, it can't be that hard.
  - yesimahuman 17y ago
    Out of my four years of college maybe one professor coded on-screen in front of us, and it was during one of the earlier classes. It's not that I don't appreciate or respect the traditional CS study, but as a programmer, how else are you really going to learn, than to watch a master at his craft? As I sit here in my last semester implementing a few chosen functions of a small but complete RDBMS for my databases class (i.e. most of the code was written, we just had to fill in stuff relating to a certain topic (buffer management, heap files, etc.)), it makes me wish that I would have seen how the whole system was developed from the first thought processes to the final debugging. That would have been a much better learning experience.
psyklic 17y ago
The best way for me to study for test was to read through a lot of worked out problems. This works great for the short term, but not for the long term. Retention from reading is a lot less than from doing. Sure, you may learn programming faster by reading lots of examples and books ... but it will discourage experimentation. You'll only learn what you read, and you will likely not understand it as in-depth. I learned programming without guidance, on my own. Having to figure everything out with only one or two books and no Internet is an invaluable experience. I really feel that going through that was my competitive advantage.
Locke1689 17y ago
I think pair programming with the beginner at the keyboard is the best thing I've worked with. As part of the student ACM chapter I've organized a lot of tutoring for non-programmers. Walking through my own thought process with the beginner in how to solve a problem seems to help a lot. For example, one thing I had to explain to a student was that figuring out how your program will work is often identical to figuring out how you yourself would do the problem (assuming you can solve the problem). One specific problem we were working involved essentially an itoa function. By using the Socratic method I managed to get the student to explain at the most basic level how they did operations on numbers. Once they got to the digit level, I handed them the well-known division + modular division algorithm for processing the digits of a number and they were able to build the solution from there. I also think that one of the most important concepts is really poorly taught in computer science. A lot of what we view as "good code" is really just a series of idioms and conventions that we have all agreed upon. As the IOCC shows, there are really no rules forcing anyone to follow these conventions. With somebody looking over their shoulder and saying, you know, we usually express this pattern as this, it basically teaches them what they would have otherwise had to spend hours reading code learning. That said, I'm not really sure what the best way to teach programming is. The most important thing one programmer can teach another is how to learn on their own, but I really have no idea how to teach that.
yummyfajitas 17y ago
While I agree that this method might help in Algebra/intro to CS, I'm not sure it's beneficial in the long run. The net result is the following set of expectations: you teach them how to apply an algorithm, then they repeat what you told them on the test. This is nothing more than "teaching to the test". This is, for the most part, how students are taught in high school. The problem is the following: real life and (if you are doing your job right) more advanced classes don't fit this model. A simple linear algebra example (from my midterm two weeks ago) illustrates what happens when students are taught this way. Problem: a 4k x 4k matrix M consists of 4x4 blocks along the diagonal, 4x4 blocks on the bottom row, and zeros elsewhere. Find an efficient algorithm for computing M v (v a vector). [ M1 0 0 ... 0 ] [ 0 M2 0 ... 0 ] [ ... ] [ B1 B2 ... Bk] The right answer consists of multiplying only the non-zero blocks and has complexity O(k). I gave partial credit for any answer that computed M v. The most common answer I got was "compute the LU factorization." Some went so far as to explain how to use the LU factorization to solve Mx = v. Apparently, I used the word "efficient" when explaining the purpose of the LU factorization, and I used the word "efficient" in this problem. My students were trained for 12 years to repeat the teachers password. This training failed them the moment they needed to think. It may improve performance in the short term, and it's an easy way to teach. But the long term results are extremely harmful.
Tycho 17y ago
My biggest complaint about programming education and text-books is the handling of the 'object-oriented' issue. They throw it at you, at the very start, with zero context. I asked my lecturer what 'non-object-oriented' programming would be, and he couldn't give me a straight answer. A fellow student turned and said 'it's like when you don't have buttons, just prompts' (with an implied 'd'uh!'). It seemed he was confusing the OO paradigm with the 'visual' programming/design paradigm. Another problem is when they teach about encapsulation, they put far too much emphasis on defensive programming and make it sound like there's hackers out to meddle with your classes or grossly negligent colleagues who MUST NEVER see your code; whereas it seems to me the main benefit is 'information hiding' for the purpose of focusing control/interfacing into single points thereby making changes easier (eg. you could have any number of possible mechanisms behind a clock-face but the face remains always familiar to the outside world). Of course, these are just my opinions as a relative n00b. :)
- extension 17y ago
  Object-orientation has got to be the most confused and abused concept in all of technology. Even the experts can't agree on exactly what it means, but that doesn't stop every other dingbat from telling you.
dctoedt 17y ago
Law schools should take note, too -- generations of 1Ls have cynically remarked that the main benefit of "Socratic method" teaching is that it allows law schools to maintain a 100:1 student:teacher ratio.

78 points by nreece 17y ago

Aren't there some good books that show an overview of what programming is all about? For example, those at http://olympiads.win.tue.nl/ioi/study/books.html http://olympiads.win.tue.nl/ioi/study/books.html include a few quite accessible books (and several more that are very hard). How about guidance into C via The Art and Science of C: A Library Based Introduction to Computer Science by Eric S. Roberts http://www.amazon.com/Art-Science-Library-Introduction-Computer/dp/0201543222/ http://www.amazon.com/Art-Science-Library-Introduction-Compu... or guidance into LISP with the famous Structure and Interpretation of Computer Programs (SICP) textbook? http://www.amazon.com/Structure-Interpretation-Computer-Programs-Engineering/dp/0262011530/ http://www.amazon.com/Structure-Interpretation-Computer-Prog...

jacoblyles 17y ago

A human teacher isn't always available to demonstrate things. How can we duplicate the experience of teaching for people with nothing but a browser and desire?

wooster 17y ago

I learned to program by reading code others had written. This was way before college. By the time I got to college, I had years of experience reading Perl scripts and very complex C networking programs. If there's one thing I would fix in CS curricula, it would be to make students read more code. When I was at Apple, I wrote a lot of software to make it easier for Apple employees to read code that other people in the company had written. That software has since been called "the most important thing to happen to software engineering at Apple, ever" by someone who is very high up in the org. chart. I have written a lot of code, and that has made me a good programmer. Reading a lot of code, however, has been even more important.

pmjordan 17y ago
When I was at Apple, I wrote a lot of software to make it easier for Apple employees to read code that other people in the company had written. This idea of improving the reading/understanding experience with software is something I've tinkered with, without much success, so your story intrigues me. If you can say & don't mind, what sort of approach does/did that software take?
mechanical_fish 17y ago
It makes sense. Writing prose works the same way. Learning to write is all about reading. One thing I've noticed is that I like to reread. I get through a lot fewer classic books than many of my obsessive-reader friends because I take time to revisit books over and over. And it occurs to me that this, too, is a key activity in writing: One must read sentences and paragraphs again and again to refine them.

10ren 17y ago

Re: examples vs problem-solving: I found that attempting a problem that was beyond me would prime my mind, so that when I read the solution, my mind would grab it. Like an enzyme. Apart from focusing on the relevant aspect of the material, it also provides motivation, and then satisfaction though tension and release. Something of a drama/sales technique. [EDIT it also combats that feeling of not having learnt anything in 3 years, by giving contrasting experiences of not-knowing and knowing. All humans are intelligent; I believe learning is just a matter of paying attention, which requires motivation and confidence. A sense of progress helps both.] I tried this on a class when I was tutoring at uni, and it seemed to work well. Students were surprisingly interested in the answers to puzzles I put on the board at the start of each tute, even though I didn't refer to them, and several did extremely well in the subject. Unfortunately, I have no comparative data with other tutes, due to "privacy issues", which averages would have overcome. So much for my dept's interest in teaching quality.

fnid2 17y ago

Extreme programming could be a better alternative. Have the experienced person solve the problem while the novice types out the solution. It's better than simply reading the solution, because you're hearing the rationale for the lines as they are being written. Writing them burns them into your brain. Perhaps we can group sophomores with freshmen. The sophomores are tasked with solving the problems and the freshmen are tasked with typing out the code. It also primes the seemingly naturally introverted programmers for group based activity that will benefit them in the long run.

swolchok 17y ago
Perhaps we can group sophomores with freshmen. The sophomores are tasked with solving the problems and the freshmen are tasked with typing out the code. It also primes the seemingly naturally introverted programmers for group based activity that will benefit them in the long run. I think this is an awful idea because the average freshman will learn from the output of the average sophomore, which is not good at all.
- techiferous 17y ago
  This is a technique that teachers use and it can be effective if done right. Of course you have to make sure the "sophomores" know what they are doing. It works for a variety of reasons, including more one-on-one time and the fact that you learn best what you teach (yes, the sophomores will be learning, too).
samdk 17y ago
At least in my case, this wouldn't have worked at all. Most of the stuff I wrote as a sophomore was orders of magnitude more complicated than what I was doing as a freshman. I wouldn't have understood what was happening at all.
- fnid2 17y ago
  That's okay. It'll be that way forever. I look at code I wrote 6 mos ago and gasp at the inefficiencies. If the freshman finds a better way, all the better -- the sophomore learns more too!

techiferous 17y ago

This reminds me of some teacher training I received a few years ago. The teacher was showing us a technique for teaching a new skill to people: * First I do it. (Step one is blah, then we do foo, etc.) * Then you help me do it. (So what's the first step? and then what do I do? etc.) * Then I help you do it. * Then you do it. The first part is important: new learners simply watching an experienced teacher applying the skill.

mbrubeck 17y ago
My best CS professors would write code on-screen during lectures (usually in a REPL, or sometimes an IDE). The great thing about watching them coding "live" is that you can see into their thought processes: which mistakes they make, how they figure out the mistakes and recover from them, exploratory code they write and throw away, the order they do things, how they evolve simple examples into complex programs. You don't get any of that from just seeing the finished product. It's also great for picking up mundane practical tips, like tab completion, GNU screen, shell history, and how to quickly look up documentation.
- branden 17y ago
  Yes, yes, yes. My favorite programming instructor would often code in front of the class on a projector. Like you I learned a bunch of little tricks, and it also built confidence. If he can write an AVL tree in front of my eyes in an hour then man, it can't be that hard.
- yesimahuman 17y ago
  Out of my four years of college maybe one professor coded on-screen in front of us, and it was during one of the earlier classes. It's not that I don't appreciate or respect the traditional CS study, but as a programmer, how else are you really going to learn, than to watch a master at his craft? As I sit here in my last semester implementing a few chosen functions of a small but complete RDBMS for my databases class (i.e. most of the code was written, we just had to fill in stuff relating to a certain topic (buffer management, heap files, etc.)), it makes me wish that I would have seen how the whole system was developed from the first thought processes to the final debugging. That would have been a much better learning experience.

psyklic 17y ago

The best way for me to study for test was to read through a lot of worked out problems. This works great for the short term, but not for the long term. Retention from reading is a lot less than from doing. Sure, you may learn programming faster by reading lots of examples and books ... but it will discourage experimentation. You'll only learn what you read, and you will likely not understand it as in-depth. I learned programming without guidance, on my own. Having to figure everything out with only one or two books and no Internet is an invaluable experience. I really feel that going through that was my competitive advantage.

Locke1689 17y ago

I think pair programming with the beginner at the keyboard is the best thing I've worked with. As part of the student ACM chapter I've organized a lot of tutoring for non-programmers. Walking through my own thought process with the beginner in how to solve a problem seems to help a lot. For example, one thing I had to explain to a student was that figuring out how your program will work is often identical to figuring out how you yourself would do the problem (assuming you can solve the problem). One specific problem we were working involved essentially an itoa function. By using the Socratic method I managed to get the student to explain at the most basic level how they did operations on numbers. Once they got to the digit level, I handed them the well-known division + modular division algorithm for processing the digits of a number and they were able to build the solution from there. I also think that one of the most important concepts is really poorly taught in computer science. A lot of what we view as "good code" is really just a series of idioms and conventions that we have all agreed upon. As the IOCC shows, there are really no rules forcing anyone to follow these conventions. With somebody looking over their shoulder and saying, you know, we usually express this pattern as this, it basically teaches them what they would have otherwise had to spend hours reading code learning. That said, I'm not really sure what the best way to teach programming is. The most important thing one programmer can teach another is how to learn on their own, but I really have no idea how to teach that.

yummyfajitas 17y ago

While I agree that this method might help in Algebra/intro to CS, I'm not sure it's beneficial in the long run. The net result is the following set of expectations: you teach them how to apply an algorithm, then they repeat what you told them on the test. This is nothing more than "teaching to the test". This is, for the most part, how students are taught in high school. The problem is the following: real life and (if you are doing your job right) more advanced classes don't fit this model. A simple linear algebra example (from my midterm two weeks ago) illustrates what happens when students are taught this way. Problem: a 4k x 4k matrix M consists of 4x4 blocks along the diagonal, 4x4 blocks on the bottom row, and zeros elsewhere. Find an efficient algorithm for computing M v (v a vector). [ M1 0 0 ... 0 ] [ 0 M2 0 ... 0 ] [ ... ] [ B1 B2 ... Bk] The right answer consists of multiplying only the non-zero blocks and has complexity O(k). I gave partial credit for any answer that computed M v. The most common answer I got was "compute the LU factorization." Some went so far as to explain how to use the LU factorization to solve Mx = v. Apparently, I used the word "efficient" when explaining the purpose of the LU factorization, and I used the word "efficient" in this problem. My students were trained for 12 years to repeat the teachers password. This training failed them the moment they needed to think. It may improve performance in the short term, and it's an easy way to teach. But the long term results are extremely harmful.

Tycho 17y ago

My biggest complaint about programming education and text-books is the handling of the 'object-oriented' issue. They throw it at you, at the very start, with zero context. I asked my lecturer what 'non-object-oriented' programming would be, and he couldn't give me a straight answer. A fellow student turned and said 'it's like when you don't have buttons, just prompts' (with an implied 'd'uh!'). It seemed he was confusing the OO paradigm with the 'visual' programming/design paradigm. Another problem is when they teach about encapsulation, they put far too much emphasis on defensive programming and make it sound like there's hackers out to meddle with your classes or grossly negligent colleagues who MUST NEVER see your code; whereas it seems to me the main benefit is 'information hiding' for the purpose of focusing control/interfacing into single points thereby making changes easier (eg. you could have any number of possible mechanisms behind a clock-face but the face remains always familiar to the outside world). Of course, these are just my opinions as a relative n00b. :)

extension 17y ago
Object-orientation has got to be the most confused and abused concept in all of technology. Even the experts can't agree on exactly what it means, but that doesn't stop every other dingbat from telling you.

dctoedt 17y ago

Law schools should take note, too -- generations of 1Ls have cynically remarked that the main benefit of "Socratic method" teaching is that it allows law schools to maintain a 100:1 student:teacher ratio.