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Age of the child I gave this to:. Hours of Play:. The following example provides a timeline for exploring line-by-line execution, and a slider for exploring frame-by-frame. This control enables the programmer to go backwards and forwards through time, study interesting frames, and compare the execution across different frames. In the above example, we are once again peeking through a pinhole, seeing just one frame at a time.
In the following example, all frames are lightly overlaid, in order to give context to the active frame. The entire path of the ball can be seen at once. The output of the program is no longer a series of fleeting moments, but can be seen as a single, solid thing that extends over time. There is great power in this way of thinking. Again, the particular solutions shown here are merely examples.
What matters is the underlying purpose: enabling the learner to follow the program flow, by controlling time and seeing patterns across time. Transforming flow from an invisible, ephemeral notion into a solid thing that can be studied explicitly. The third line declares a variable named "scaleFactor", which varies with each iteration of the loop.
Wait a minute. Were you trying to answer those questions by doing arithmetic in your head? The computer somehow drew that picture, so the computer must have calculated all those scaleFactors itself. Are you seriously recalculating them in your head? Now imagine if scaleFactor also depended on some other variables, or some other functions, or external input.
There would be no way to easily answer those questions. Think about this. We expect programmers to write code that manipulates variables, without ever seeing the values of those variables.
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The entire purpose of code is to manipulate data, and we never see the data. We write with blindfolds, and we read by playing pretend with data-phantoms in our imaginations. Information design pioneer Edward Tufte has one primary rule, and this rule should be the principle underlying any environment for creating or understanding. If you are serious about creating a programming environment for learning, the number one thing you can do -- more important than live coding or adjustable constants, more important than narrated lessons or discussion forums, more important than badges or points or ultra-points or anything else -- is to show the data.
Because the value of a variable varies over time, showing the data is intimately connected with showing time.
The previous section presented a timeline representation that showed the data at each step. In the following example, the programmer mouses over a particular row of the timeline to concentrate on a single line. In this example, it is easy to answer the first two questions.
By skimming over the execution of that line of code, we can see all of the values that scaleFactor takes on, and when. However, it is still difficult to answer the third question: how does the variable vary? What is the shape of its change? The question is difficult because we are, once again, peeking through a pinhole, only seeing a single point at a time. Edward Tufte has a second rule. It is not enough to just show the data.
We must show comparisons.
Data needs context. It is rarely enough to see a single data point in isolation. We understand data by comparing it to other data. The timeline examples so far have used dots to represent executed lines. But instead of dots, we can show data. The following timeline shows each of the scaleFactors:. Almost every line of code here calculates something. The environment should provide the best visualization of whatever that something is.
For example, the "rotate" line can show the rotations. The "triangle" line draws a triangle to the canvas, rotated and colored. The timeline can show a thumbnail of each triangle produced. Taken together, we have a timeline that depicts not just the flow, but all of the data calculated in that flow.
The execution of the program is laid bare for the reader. At a glance, she can see which lines were executed, when they were executed, and what they produced.
The flow and the data are both shown in context. The example above only loops twenty times. Is it possible to understand a loop with, say, thousands of iterations, without drowning in thousands of numbers? Yes -- there is an entire field of study devoted to depicting large amounts of numbers.au.ezifopusovoj.tk
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To visualize this data, we can use all of the standard techniques of data visualization. In the following example, as the programmer zooms the timeline out, the visualization automatically switches from a table to a plot.
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In order to understand what a line of code does, the learner must see its effect. For example, as the programmer moves over iterations of the "triangle" line, she sees each triangle appear on the canvas:. The "fill" line, on the other hand, sets the fill color for subsequent drawing operations. When the programmer moves over this line, what effect does she see?