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3aab9f lisa 2026-08-11 23:24:06
Add C06 skill-code study pages, linked from the SD hub Eleven pages ported from the applied-computing-au C06-Reference-Godot standard: home page with the 34-code lookup, per-topic pages with labelled GDScript examples, evidence standards, and Check Your Understanding fold blocks. Generated mirror — repo copy is canonical. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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<!-- Generated from applied-computing-au vic/unit3-4/sat/C06-2026/C06-Reference-Godot — do not hand-edit; re-run the port. -->
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# Local and Global Variables — GDScript
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**Skill codes on this page**
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| Code | Level | Skill |
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|---|---|---|
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| C621 | 3–4 | local variables |
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| C622 | 3–4 | constants |
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| C628 | 3–4 | uses data types for local variables |
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| C631 | 5–6 | global variables |
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| C634 | 5–6 | uses appropriate data types for global variables |
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**Definition.** A *variable* stores and labels data to be referenced and manipulated in a program. Its **scope** is the part of the program that can see it.
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| | Where it is written | Who can see it |
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|---|---|---|
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| **Local (C621)** | Inside a function | Only that function |
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| **Global (C631)** | Outside every function, at script level | Every function in the script |
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**Quick check:** is the line indented inside a `func`? Local.
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## C621 — Local variables
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**Definition.** Variables defined inside a function that can only be accessed by that function.
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```gdscript
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func calculate_fare() -> void:
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# C621 — local variable: only calculate_fare() can see it
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var fare: float = 5.30
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balance -= fare
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```
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Parameters and loop variables are local too — in `connect-go-dots/grid.gd`, the parameter `photo: Texture2D` and the loop variable `button` exist only inside their function.
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## C631 — Global variables
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**Definition.** Variables defined outside any function that can be accessed by all functions throughout the source code.
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At the script level:
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```gdscript
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extends Control
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# C631 — global variables: every func in this script can use them
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var balance: float = 20.00
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var is_concession: bool = false
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```
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Or using `class_name` with `static` for access from other scripts:
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```gdscript
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class_name GlobalVars
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static var g_var = 20 # C631 — global via class_name
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```
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An **autoload singleton** is the Godot-idiomatic project-wide global — if you use one, name it as your C631 evidence in validation.
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**In connect-go-dots** — the autoload in action (`shared.gd`, registered as `Shared`):
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```gdscript
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# connect-go-dots — shared.gd (autoload "Shared")
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extends Node
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## Handed from one screen to the next. Lives on root, so a scene change
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## cannot touch it.
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var photo: Texture2D # C631 — global: both screens use it
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```
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```gdscript
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Shared.photo = photo # C631: grid.gd — one screen writes it
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%Photo.texture = Shared.photo # C631: detail.gd — the other reads it
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```
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The `##` comment is model internal documentation: it says *why* the variable lives where it does.
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## C622 — Constants
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**Definition.** A fixed value that, once defined, cannot be altered during the execution of a program.
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```gdscript
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# C622 — constant: the daily cap never changes while the program runs
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const DAILY_CAP: float = 9.60
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```
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**Earns the tick:** `const` used for a value that genuinely never changes, named in CAPITALS. Showing Godot's error when you try to assign to it is a neat validation demo.
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## C628 and C634 — choosing the right data type
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C621/C631 is that the variable **exists**. C628/C634 is that its data type **suits the data** — C628 for locals, C634 for globals.
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```gdscript
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extends Control
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var trips_today: int = 0 # C634 — int: you cannot take half a trip
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var balance: float = 20.00 # C634 — float: money needs decimal places
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var is_concession: bool = false # C634 — bool: only two possible answers
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var card_id: String = "" # C634 — String: digits never used in a calculation
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func charge(zone: int) -> void:
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var fare: float = FARE_TABLE[zone] # C628 — float: fares have cents
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balance -= fare
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```
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From tile-matching-game (`deck.gd`):
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```gdscript
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# tile-matching-game — deck.gd
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var key: String = card["pair"] # C628 — String: the pair label from the CSV
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```
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**State the data type.** `var trips_today = 0` cannot earn C634 because no data type has been given for the marker to assess. Always write `: int`, `: float`, `: bool` or `: String`.
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`var trips_today := 0` is acceptable — GDScript works out the type for you — but name it in your comment so the marker can see it: `# C634 — int: you cannot take half a trip`.
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Types go beyond `int`/`float`/`bool`/`String`: in connect-go-dots the global is `var photo: Texture2D` — same standard, `# C634 — Texture2D: the value is an image`.
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The **why** in these comments doubles as your reasoning evidence (C629/C638) — see [Data Types](/sd/C06/Data%20Types).
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## Check Your Understanding
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1. `var speed := 5` at script level — which code does it earn as written, and what more would C634 need?
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>| ### Answer
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>| C631 (a global exists). C634 needs the type visible — write `: int`, or name it in the comment — plus the *why*.
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2. Are function parameters local or global?
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>| ### Answer
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>| Local (C621): they exist only inside their function.
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3. What three things make a C622 constant?
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>| ### Answer
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>| `const`, a CAPITALS name, and a value that genuinely never changes while the program runs.