Lesson 9 of 11
The big picture
Show on a big screenThe eight ideas, in order.
| Idea | Remember | Example |
|---|---|---|
| Typing it out | One line, one instruction, top to bottom. | Swap two lines, order changes |
let and const | let refills. const refuses and names the box. | seats stays 32 |
| Four kinds of value | Number, text, true or false, nothing. | 12 vs "12" |
| What the signs do | Arithmetic on numbers. + joins when the other side can be written out. | 163 → "163 rupees" |
| A fork in the line | if runs only when true. else catches the rest. | 60 ≥ 60 is true |
| Until it stops | while checks first, then runs, then checks again. | 96 → 6 in 4 rounds |
| Once for each | for ... of runs once per item in the list. | 3 stops, 3 turns |
| What the message says | A line number, and what could not be done there. The cause may sit above it. | line 3, missing let |
A machine does exactly what you typed, and nothing else. So its message tells you where it stopped.
Next comes Computational Thinking III: Functions & Debugging. One set of lines gets a name. A wrong program is checked in halves, not read from the top.