<p>There may be a psychological-physiological learning advantage to having students see solutions or code presented at nearly the same rate as the student would write or type in the code themselves.</p>

<p>Having N steps appear (especially if it exceeds 7+-2 cognitive units), all at once, might overload a student's short term memory, and thus can result in some of the information being nearly invisible, and thus harder to learn from that projection.</p>

<p>An alternative would be to use presentation software to animate the projection so that the code (or algorithms, etc.) appears sequentially in time at a slow enough rate to talk through each step or component.</p>

CC BY-SA 3.0
2017-06-17T20:50:23.193Z
2017-06-17T20:50:23.193Z
hotpaw2
<p>I'm working in TCS, so my lectures are relatively mathematical.
For me, it's a rather clear split:</p>

<ul>
<li>Definitions, Inference Systems, etc.: Projector (+ lecture notes)</li>
<li>Lemmas, Theorems: Projector (+ lecture notes)</li>
<li>Proofs: Blackboard (+ lecture notes)</li>
<li>Examples: Blackboard</li>
</ul>

<p>The advantages:</p>

<ul>
<li>I save some time compared to a blackboard-only lecture.</li>
<li>I can refer to definitions and lemmas on the projector while presenting proofs or examples on the blackboard (while proving Thm. 3.7: "... and now we can use Lemma 3.4 <em>[shows Lemma 3.4 on the projector]</em> and we get a contradiction ...")</li>
<li>I have the necessary amount of space for proofs (much more than using a projector).</li>
<li>I present proofs and examples at a reasonable speed.</li>
<li>I can point to the blackboard with my hands, which is much more effective than using a laser pointer ("... and now we compare this subterm <em>[marks some text with the left hand]</em> and that subterm <em>[marks some text with the right hand]</em> ...").</li>
<li>I can improvise examples whenever necessary.</li>
</ul>

CC BY-SA 3.0
2017-06-16T17:11:08.930Z
@nocomprende Fortunately, my projector and my blackboard don't overlap too much. (If you can't use them in parallel it sucks.)
Uwe
CC BY-SA 3.0
2017-06-16T16:40:39.313Z
2017-06-16T16:50:28.800Z
2017-06-16T16:50:28.800Z
Uwe
<p>Shifting to the blackboard/whiteboard from the projector serves two main purposes:</p>

<ul>
<li><p><strong>Slows down the pace of instruction.</strong> I can type much faster than I can write on the whiteboard. However, this is not always a good thing. When I'm discussing something complex or want to ensure my instruction does not move too quickly, I shift to writing things out. This forces me to be more thoughtful with timing and often times has prevented me from giving students more information than was necessary for a particular lesson.</p></li>
<li><p><strong>Shifts focus from code to concept.</strong> As I say in a lot of my answers, differentiation is key. Staring at code to understand a concept is not always going to make it sink in. By writing on the board, I often times can draw close attention to a concept (i.e. recursion or variables) outside of its context within a program. When introducing something new and/or something complex, this helps me ensure that students understand the <em>thing</em> before they code that <em>thing</em>. For example, with recursion, I draw out stack frames, naming each one with its function name and arguments and drawing arrows with values passed in and values returned. The magic of a few lines of code that calculates a factorial becomes a little less opaque when there's a visual abstraction to which students can connect the code. Additionally, introducing variable assignment to beginners, especially something like <code>x = x + 1;</code>, works well on the whiteboard where I can number the steps, translate it into "English" underneath, use different colors, etc. </p></li>
</ul>

<p><strong>Bonus</strong>: It's not always a game of either/or. Projecting code onto a whiteboard mixes the modalities: students can see "real code," but that same code can then be analyzed and annotated by hand.</p>

<p>For my own unique context in a classroom with whiteboard-top desks, I can have students write down what I write down when I use the whiteboard. It becomes a shared task since we are all doing the same thing and forces me outside of the "sage on the stage" paradigm for a minute. Instead of lecture and fast-typing, I can participate along with them in writing on a whiteboard. This has as much to do with engagement and classroom environment as it does with pedagogy.</p>

CC BY-SA 3.0
2017-06-17T21:01:12.903Z
Whiteboard desks are awesome. Mine aren't specifically whiteboard painted but they work with dry erase markers. I have an Expo marker on me all the time and can write on the desk to help.
Ryan Nutt
CC BY-SA 3.0
2017-06-16T16:18:57.297Z
2017-06-16T16:21:04.577Z
2017-06-16T16:21:04.577Z
Peter
<p>My poor blackboard<sup><strong>1</strong></sup> only gets light use nowadays, I'm afraid.  Coding examples are usually too large to put up there, all of my intricate diagrams are clarified with (judicious!) animations in PowerPoint, and my debugging gets demonstrated live on the projector screen.  The humble blackboard has seen its role reduced in CS classrooms as the years have gone by.</p>

<p>It still has its place, though!  Improvised diagrams go up there, such as when a student asks an unexpected question about a linked list.  And pulling a struggling kid up to the board (during individual work time, <em>not as some form of humiliation)</em> can give us space, both mental and physical, to work through a conceptual problem together.</p>

<p>Of course, in more advanced CS coursework, we start veering back towards the mathematical, where the blackboard is still king.  Well, maybe not the king anymore, but at least a Marquess or an Earl.  Working through problems and proofs at the blackboard keeps the pace slower than a PowerPoint and gives the students that much more time to absorb the material, and asking students to write up the answers to in-class questions allows us to have class discussions around the results.</p>

<p>And there's one more place where the board comes in handy: harder labs, especially the kind that kids have a hand in designing themselves.  <em>I've found that my students naturally gravitate to the board when they need to brainstorm or work through a particularly tricky problem.</em>  Something about having all that space to think and try frees the mind.  Paper just doesn't seem to do this same trick.</p>

<p><em>The blackboard may be dying, but it ain't dead yet.</em></p>

<p><sup><strong>1</strong></sup> Okay, technically I use a whiteboard in my classroom. I'd prefer a blackboard, but I don't get that choice in real life. But I get my choice here and now, in this very answer, and <em>blackboard, I choose you.</em></p>

CC BY-SA 3.0
2017-06-16T14:27:25.577Z
+1 Improvising is something I often find easier with a blackboard than with computer tools (for example, modifying a presentation).
TuringTux
CC BY-SA 3.0
2017-06-16T14:27:37.353Z
I liked the reference at the last sentence in the footnote ;)
ItamarG3
CC BY-SA 3.0
2017-06-16T14:25:43.340Z
2017-06-16T14:25:43.340Z
Ben I.
<p>The last time I used a whiteboard as a whiteboard was to describe a maze building algorithm. It was a small-ish board that I put on the ground and drew a grid. I then stepped in a square and we walked (literally and algorithmically) through the algorithm where I built the maze. </p>

<p>The whiteboard on the front of my room gets used sometimes when I want to write over examples. I'll project and then annotate what's there. But that's rare, and it's usually covered up with a large projector screen. </p>

<p>Of course, my handwriting is terrible and my classroom is large enough that it's tough to see anything I write from the back. So that's probably part of the reason. </p>

<p>Somewhat related story here...</p>

<p>When I interviewed, before I saw the classroom, the AP that was interviewing me was very apologetic that there wasn't a Smartboard in the classroom. They had just gone through a rebuild and reconfigured most of the classrooms, and most had a Smartboard. Mine had "just a normal screen." When I walked in I was good with the screen. It's almost floor to ceiling and covers probably 80% of the width of my room. Much better than a little Smartboard. </p>

CC BY-SA 3.0
2017-06-16T15:41:09.840Z
2017-06-16T15:41:09.840Z
Ryan Nutt
<p>One example is the front end web development concept of the box model. For those who do not know what the box model is, here is a graphic:</p>

<p><a href="https://i.sstatic.net/uWkEw.gif" rel="nofollow noreferrer"><img src="https://i.sstatic.net/uWkEw.gif" alt="The box model"></a></p>

<p>I find that there is no real way to explain it without drawing it out. Usually, when I teach this, I've already covered basic HTML and CSS syntax, including a few properties (e.g. <code>background</code>). I like to give the example of creating a span with some text inside, so I draw on the board:</p>

<pre><code>Hello Class!
</code></pre>

<p>I'll then explain that the browser sees that as the "content" of the element, and draws a box around it, so I draw a box around it:</p>

<pre><code>|---------|
| Content |
|---------|
</code></pre>

<p>I'll also point out that the browser draws a box around the entire element:</p>

<pre><code>|-----------------|
|                 |
|   |---------|   |
|   | Content |   |
|   |---------|   |
|     Element     |
|-----------------|
</code></pre>

<p>Then I'll explain that the browser need to how much space to give the element on the outside and how much space it needs to give the content, which introduces padding and margin, and finally I'll add a border, finishing my explanation.</p>

CC BY-SA 3.0
2017-06-16T14:21:34.533Z
I find this is a good usage of a blackboard, but I think (I'm not at all sure of this) that chrome can show this for a website when you press F-12...
ItamarG3
CC BY-SA 3.0
2017-06-16T14:22:49.280Z
@ItamarGreen Yeah, most dev tools in your browser will show it, but a) it's small and b) I don't want to just show the picture, the blackboard helps me _explain_ it.
thesecretmaster
CC BY-SA 3.0
2017-06-16T14:23:13.770Z
Which is why this is a good answer ;)
ItamarG3
CC BY-SA 3.0
2017-06-16T14:19:47.947Z
2017-06-16T14:19:47.947Z
thesecretmaster
<p>You can use a blackboard with a fun on board example:</p>

<p>A good way to explain what the computer does while executing a recursive method, is to debug a (simple) recursive method. This is done by hand (on the blackboard) by going through the method line by line, and with every recursive call, going down 1 line (on the board) and indenting. Then going through the method line by line, with the parameters passed from the recursive call. </p>

<p>This is done recursively, and when a <code>return</code> statement is met, you go down 1 line (again, on the board) and "unindent". </p>

<p>This is great way to explain recursion. The students see on the board the process done by the computer. While drawing it on a computer and projecting it does show the final result, the process itself might be lost on the students.</p>

<p>There is also some value to seeing how the call stack works, but that's a side bonus. </p>

<p>Another nice bonus to this is a situation where one runs out of space while going down lines on the board. That's when the instructor should turn dramatically towards the students and say "And that, is what <em>stack overflow</em> means."</p>

CC BY-SA 3.0
2017-06-16T14:23:17.033Z
If the end of the board is reached while indenting, you could even explain a stack overflow with this.
TuringTux
CC BY-SA 3.0
2017-06-16T14:23:58.787Z
@TuringTux good point. Thanks (I'll add it to the answer. Do you want me to give you credit for that?)
ItamarG3
CC BY-SA 3.0
2017-06-16T14:25:20.837Z
No, you don't need to :) Nice to see I could bring in something valuable.
TuringTux
CC BY-SA 3.0
2017-06-16T14:19:57.313Z
2017-06-16T14:29:09.510Z
2017-06-16T14:29:09.510Z
ItamarG3
<p>These days, we've got all this fancy, new-fangled technology. We've got live coding, we've got presentations, we've got remote desktop adapted for classroom use. There seems to be a tool for every teaching problem. But when should we ignore the KnowledgeInjector<strong>2000</strong><sup>TM</sup> and instead use the good old blackboard?</p>

<p>More specifically, which concepts are easier to explain with a blackboard and how would you use a blackboard to explain them?</p>

CC BY-SA 3.0
2017-06-16T15:57:23.193Z
Does it have to be black board, or would you like other unplugged ideas?
ctrl-alt-delor
CC BY-SA 3.0
2017-06-16T16:51:36.977Z
@richard Based on the context of this question (and the presence of other unplugged discussions), I think this question specifically focuses on projector v. board.
Peter
CC BY-SA 3.0
2017-06-16T17:02:13.590Z
Alternatives I've seen are using a tablet pen to write/draw on-screen, and a desk-mounted camera to project writing from a sheet of paper. Both were far more readable than a blackboard in a large lecture theatre where many students can be sitting far back.
Bob
CC BY-SA 3.0
2017-06-17T23:22:15.227Z
Just leaving these links here; anyone feel free to turn them into an answer if appropriate: [Psychophysiology of blackboard teaching](https://micromath.wordpress.com/2010/09/24/psychophysiology-of-blackboard-teaching-2/) by Borovik, [Still Like That Old-Time Blackboard Talk](http://sites.math.rutgers.edu/~zeilberg/Opinion60.html) by Zeilberger.
ShreevatsaR
<classroom-infrastructure>
When should I scrap my projector for a blackboard?
# When should I scrap my projector for a blackboard?

(Asked by: username_0 on 2017-06-16)

These days, we've got all this fancy, new-fangled technology. We've got live coding, we've got presentations, we've got remote desktop adapted for classroom use. There seems to be a tool for every teaching problem. But when should we ignore the KnowledgeInjector**2000**TM and instead use the good old blackboard?

More specifically, which concepts are easier to explain with a blackboard and how would you use a blackboard to explain them?

**Tags:** classroom-infrastructure

> **Comments:**
> **username_1**: Does it have to be black board, or would you like other unplugged ideas?  
> **username_2**: @richard Based on the context of this question (and the presence of other unplugged discussions), I think this question specifically focuses on projector v. board.  
> **username_3**: Alternatives I've seen are using a tablet pen to write/draw on-screen, and a desk-mounted camera to project writing from a sheet of paper. Both were far more readable than a blackboard in a large lecture theatre where many students can be sitting far back.  
> **username_4**: Just leaving these links here; anyone feel free to turn them into an answer if appropriate: [Psychophysiology of blackboard teaching](https://micromath.wordpress.com/2010/09/24/psychophysiology-of-blackboard-teaching-2/) by Borovik, [Still Like That Old-Time Blackboard Talk](http://sites.math.rutgers.edu/~zeilberg/Opinion60.html) by Zeilberger.  

---

## 7 answers

### Answer by username_2 on 2017-06-16. Score: 13

Shifting to the blackboard/whiteboard from the projector serves two main purposes:

* **Slows down the pace of instruction.** I can type much faster than I can write on the whiteboard. However, this is not always a good thing. When I'm discussing something complex or want to ensure my instruction does not move too quickly, I shift to writing things out. This forces me to be more thoughtful with timing and often times has prevented me from giving students more information than was necessary for a particular lesson.
* **Shifts focus from code to concept.** As I say in a lot of my answers, differentiation is key. Staring at code to understand a concept is not always going to make it sink in. By writing on the board, I often times can draw close attention to a concept (i.e. recursion or variables) outside of its context within a program. When introducing something new and/or something complex, this helps me ensure that students understand the *thing* before they code that *thing*. For example, with recursion, I draw out stack frames, naming each one with its function name and arguments and drawing arrows with values passed in and values returned. The magic of a few lines of code that calculates a factorial becomes a little less opaque when there's a visual abstraction to which students can connect the code. Additionally, introducing variable assignment to beginners, especially something like `x = x + 1;`, works well on the whiteboard where I can number the steps, translate it into "English" underneath, use different colors, etc.

**Bonus**: It's not always a game of either/or. Projecting code onto a whiteboard mixes the modalities: students can see "real code," but that same code can then be analyzed and annotated by hand.

For my own unique context in a classroom with whiteboard-top desks, I can have students write down what I write down when I use the whiteboard. It becomes a shared task since we are all doing the same thing and forces me outside of the "sage on the stage" paradigm for a minute. Instead of lecture and fast-typing, I can participate along with them in writing on a whiteboard. This has as much to do with engagement and classroom environment as it does with pedagogy.

> **Comments:**
> **username_7**: Whiteboard desks are awesome. Mine aren't specifically whiteboard painted but they work with dry erase markers. I have an Expo marker on me all the time and can write on the desk to help.  

---

### Answer by username_6 on 2017-06-16. Score: 10

I'm working in TCS, so my lectures are relatively mathematical.
For me, it's a rather clear split:

* Definitions, Inference Systems, etc.: Projector (+ lecture notes)
* Lemmas, Theorems: Projector (+ lecture notes)
* Proofs: Blackboard (+ lecture notes)
* Examples: Blackboard

The advantages:

* I save some time compared to a blackboard-only lecture.
* I can refer to definitions and lemmas on the projector while presenting proofs or examples on the blackboard (while proving Thm. 3.7: "... and now we can use Lemma 3.4 *[shows Lemma 3.4 on the projector]* and we get a contradiction ...")
* I have the necessary amount of space for proofs (much more than using a projector).
* I present proofs and examples at a reasonable speed.
* I can point to the blackboard with my hands, which is much more effective than using a laser pointer ("... and now we compare this subterm *[marks some text with the left hand]* and that subterm *[marks some text with the right hand]* ...").
* I can improvise examples whenever necessary.

> **Comments:**
> **username_6**: @nocomprende Fortunately, my projector and my blackboard don't overlap too much. (If you can't use them in parallel it sucks.)  

---

### Answer by username_8 on 2017-06-16. Score: 6

My poor blackboard**1** only gets light use nowadays, I'm afraid. Coding examples are usually too large to put up there, all of my intricate diagrams are clarified with (judicious!) animations in PowerPoint, and my debugging gets demonstrated live on the projector screen. The humble blackboard has seen its role reduced in CS classrooms as the years have gone by.

It still has its place, though! Improvised diagrams go up there, such as when a student asks an unexpected question about a linked list. And pulling a struggling kid up to the board (during individual work time, *not as some form of humiliation)* can give us space, both mental and physical, to work through a conceptual problem together.

Of course, in more advanced CS coursework, we start veering back towards the mathematical, where the blackboard is still king. Well, maybe not the king anymore, but at least a Marquess or an Earl. Working through problems and proofs at the blackboard keeps the pace slower than a PowerPoint and gives the students that much more time to absorb the material, and asking students to write up the answers to in-class questions allows us to have class discussions around the results.

And there's one more place where the board comes in handy: harder labs, especially the kind that kids have a hand in designing themselves. *I've found that my students naturally gravitate to the board when they need to brainstorm or work through a particularly tricky problem.* Something about having all that space to think and try frees the mind. Paper just doesn't seem to do this same trick.

*The blackboard may be dying, but it ain't dead yet.*

**1** Okay, technically I use a whiteboard in my classroom. I'd prefer a blackboard, but I don't get that choice in real life. But I get my choice here and now, in this very answer, and *blackboard, I choose you.*

> **Comments:**
> **username_9**: +1 Improvising is something I often find easier with a blackboard than with computer tools (for example, modifying a presentation).  
> **username_10**: I liked the reference at the last sentence in the footnote ;)  

---

### Answer by username_7 on 2017-06-16. Score: 4

The last time I used a whiteboard as a whiteboard was to describe a maze building algorithm. It was a small-ish board that I put on the ground and drew a grid. I then stepped in a square and we walked (literally and algorithmically) through the algorithm where I built the maze.

The whiteboard on the front of my room gets used sometimes when I want to write over examples. I'll project and then annotate what's there. But that's rare, and it's usually covered up with a large projector screen.

Of course, my handwriting is terrible and my classroom is large enough that it's tough to see anything I write from the back. So that's probably part of the reason.

Somewhat related story here...

When I interviewed, before I saw the classroom, the AP that was interviewing me was very apologetic that there wasn't a Smartboard in the classroom. They had just gone through a rebuild and reconfigured most of the classrooms, and most had a Smartboard. Mine had "just a normal screen." When I walked in I was good with the screen. It's almost floor to ceiling and covers probably 80% of the width of my room. Much better than a little Smartboard.


---

### Answer by username_0 on 2017-06-16. Score: 4

One example is the front end web development concept of the box model. For those who do not know what the box model is, here is a graphic:

I find that there is no real way to explain it without drawing it out. Usually, when I teach this, I've already covered basic HTML and CSS syntax, including a few properties (e.g. background). I like to give the example of creating a span with some text inside, so I draw on the board:
Hello Class!

I'll then explain that the browser sees that as the "content" of the element, and draws a box around it, so I draw a box around it:
|---------|
| Content |
|---------|

I'll also point out that the browser draws a box around the entire element:
|-----------------|
|                 |
|   |---------|   |
|   | Content |   |
|   |---------|   |
|     Element     |
|-----------------|

Then I'll explain that the browser need to how much space to give the element on the outside and how much space it needs to give the content, which introduces padding and margin, and finally I'll add a border, finishing my explanation.

> **Comments:**
> **username_10**: I find this is a good usage of a blackboard, but I think (I'm not at all sure of this) that chrome can show this for a website when you press F-12...  
> **username_0**: @ItamarGreen Yeah, most dev tools in your browser will show it, but a) it's small and b) I don't want to just show the picture, the blackboard helps me _explain_ it.  
> **username_10**: Which is why this is a good answer ;)  

---

### Answer by username_10 on 2017-06-16. Score: 3

You can use a blackboard with a fun on board example:

A good way to explain what the computer does while executing a recursive method, is to debug a (simple) recursive method. This is done by hand (on the blackboard) by going through the method line by line, and with every recursive call, going down 1 line (on the board) and indenting. Then going through the method line by line, with the parameters passed from the recursive call.

This is done recursively, and when a `return` statement is met, you go down 1 line (again, on the board) and "unindent".

This is great way to explain recursion. The students see on the board the process done by the computer. While drawing it on a computer and projecting it does show the final result, the process itself might be lost on the students.

There is also some value to seeing how the call stack works, but that's a side bonus.

Another nice bonus to this is a situation where one runs out of space while going down lines on the board. That's when the instructor should turn dramatically towards the students and say "And that, is what *stack overflow* means."

> **Comments:**
> **username_9**: If the end of the board is reached while indenting, you could even explain a stack overflow with this.  
> **username_10**: @username_9 good point. Thanks (I'll add it to the answer. Do you want me to give you credit for that?)  
> **username_9**: No, you don't need to :) Nice to see I could bring in something valuable.  

---

### Answer by username_5 on 2017-06-17. Score: 1

There may be a psychological-physiological learning advantage to having students see solutions or code presented at nearly the same rate as the student would write or type in the code themselves.

Having N steps appear (especially if it exceeds 7+-2 cognitive units), all at once, might overload a student's short term memory, and thus can result in some of the information being nearly invisible, and thus harder to learn from that projection.

An alternative would be to use presentation software to animate the projection so that the code (or algorithms, etc.) appears sequentially in time at a slow enough rate to talk through each step or component.


---

