We're now going to look at the code that makes up the blackjack program here in the code editor on the left-hand side of the screen.

Normally, the code editor will look like this - with the language shown determined by this menu - for example C#, or Python.

But I am going to switch to the quad editor view, so that all four languages are shown at the same time, with the live editor - Python in this case - being the top-left.

To explore the code or edit it, we need the editor to have the browser's focus - indicated by the white background. 

If the editor has a blue tint then it doesn't have focus.

To give it focus, mouse-click in blank space, or press Control e - for editor - on the keyboard

Code is made up of instructions. 

Most instructions occupy a single line and if you click anywhere within the code the whole instruction is highlighted in blue.

However, when some instructions are selected the highlight extends beyond the line. 

These are called 'compound' instructions - because they contain other instructions - indicated by the vertical bar - and in some languages
by a another horizontal part at the end.

A complete program might take only a dozen instructions - though it could be many more. 

Notice that the instructions are numbered, and that the number of instructions in the program is always identical across the four languages.

But there only a few different kinds of instruction and each of these kinds has a name. 

Depending on the language, the name might be indicated either by a keyword at the start of the instruction, and/or by a text label at the end.

This, for example, is a variable definition, and this is an if instruction. 

The syntax of the instruction differs between the languages, but the name, and the purpose of an instruction is the same across all four languages.

And if you select an instruction in the active editor pane, the corresponding instruction in the other languages is also selected - with the same number.

In some cases, the name of the instruction corresponds to the keyword at the start of the line - for example this while instruction.

In other cases, the name of the kind of instruction is given a label at the right hand end - for example here.

And all of this can be done just through the keyboard instead of the mouse. For example, cursor up and down will move the selection.

Also, we can use the home and end keys, but notice that my movement here is constrained. To only moving at the same level of indentation.

If I want to go to the owning compound instruction, I just use the cursor left key. And out again would move to the main.

And cursor right moves me to the first instruction within a compound instruction.