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The Concept

Let’s walk through our requirements and see where that leads us.

A programming environment and runtime that is easy to understand and play with.

To promote playing and experimentation, we want it to be;

Self-contained

Requiring the user to use and start different programs in an existing operating system such as windows has a few problems;

It is hard to gain an understanding about how things work together.

There is too much noise; features of different systems and programs that are not relevant to the programming process.

It is easy to get distracted.

We want a fullscreen experience that the user does not have to switch out of.

A good target device is a Raspberry PI running in console mode (X11 not booted); here it is not even possible do start a web browser to do something else.

Coherent

We want the environment to have some underlying "metaphor" that promotes understanding of the system. This is where the VHC comes in.

Let’s illustrate this with an example on how understanding can come from a coherent underlying "hardware";

Example: Learning how text works

print("What is your name? ")
name = readln()
println("Hello #{name}")

The user notices that letters are ouput from left to right, and from top to bottom.

She starts to understand the concept of a "cursor position" that is increased as text is output.

Note
 A harder concept that the user probably does not understand at this point is blocking IO; what is really happening inside readln() ? 
text 0,0, "top of the screen"
x = 0
loop {
   text x,2,"Moving text", Color::RED
   x = x + 1
   sleep 0.1
}

The user learns that text output takes place on a grid, and that it is possible to place characters anywhere on that grid. She also learns that the each "cell" in this grid can have different colors.

img = Image.from_file("ball.png")
console.define_tile('o', img)
# Display a ball image in the top left corner
console.text(0,0, 'o')

The user learns that characters are just images, and using tiles as letters is just a special case — and that the image representation of any tile can be changed.