<!-- Generated from applied-computing-au vic/unit3-4/sat/C06-2026/C06-Reference-Godot by port-reference-godot-to-wiki.py — do not hand-edit; re-run the port. -->
# Instructions and Operators — GDScript


**Skill codes on this page**

| Code | Level | Skill |
|---|---|---|
| C611 | 1–2 | instructions |
| C612 | 1–2 | arithmetic operators |
| C623 | 3–4 | logical operators |
| C624 | 3–4 | conditional operators |

## C611 — Instructions

**Definition.** A unit of code that can be executed by a compiler or interpreter.

Label a short piece of code that *does something*: takes input, calculates, produces output.

```gdscript
trips_today += 1  # C611 — instruction: updates the trip counter
```

From a studied project:

```gdscript
# connect-go-dots — grid.gd
Shared.photo = photo   # C611 — instruction: stores the chosen photo
```

**Earns the tick:** any labelled statement that executes and has an effect. This is the floor of the ladder — every student should have it.

## C612 — Arithmetic operators

**Definition.** A symbol that performs basic mathematical operations such as addition, subtraction, multiplication and division.

GDScript: `+` `-` `*` `/` `%` (remainder) and `**` (power).

```gdscript
# C612 — arithmetic operators
var total: float = fare * trips + 0.50   # * multiply, + add
var change: float = payment - total      # - subtract
var per_trip: float = total / trips      # / divide
var minutes_left: int = seconds % 60     # % remainder
```

**In tile-matching-game** (`game.gd`) — working out the board:

```gdscript
# tile-matching-game — game.gd
var total_cards := rows * columns   # C612 — * multiply
if total_cards % 2 != 0:            # C612 — % remainder: an odd board cannot hold pairs
    return
pairs_to_find = total_cards / 2     # C612 — / divide (int ÷ int stays int)
```

**Watch:** integer division truncates — `7 / 2` is `3`, but `7.0 / 2` is `3.5`. Being able to say why is C629 territory.

## C623 — Logical operators

**Definition.** A Boolean operator used to combine expressions, such as AND, OR.

GDScript uses the words `and`, `or`, `not` (the symbols `&&`, `||`, `!` also work — prefer the words).

```gdscript
# C623 — logical operators
if is_concession and zone <= 2:      # and: both must be true
    fare *= 0.5

if not card_registered or balance < 0.0:   # not, or
    show_warning()
```

**In tile-matching-game** (`game.gd`):

```gdscript
# tile-matching-game — game.gd
if is_busy or card.is_face_up or card.is_matched:   # C623 — or: any reason to ignore the click
    return

if pairs_to_find > 0 and score >= pairs_to_find:    # C623 — and: both needed to win
    message_label.text = "All pairs found in %d turns!" % turns
```

**Earns the tick:** a condition that *combines* expressions. A bare `if balance >= fare:` is C624 only — no logical operator in sight.

## C624 — Conditional operators

**Definition.** A symbol used to compare two values within a condition: equals `==`, not equals `!=`, greater than `>`, less than `<`, greater than or equal `>=`, less than or equal `<=`. Used inside selection and iteration conditions to decide whether a branch runs or a loop continues.

```gdscript
# C624 — conditional operators
if balance >= fare:      # >= at least enough money
    touch_on()
elif balance == 0.0:     # == exactly empty
    show_topup_prompt()
```

**In tile-matching-game** (`game.gd`) — the heart of the game is one comparison:

```gdscript
# tile-matching-game — game.gd
if first_card.pair_id == second_card.pair_id:   # C624 — ==: the cards match
    _handle_match()
```

**Not to be confused with** the ternary conditional *expression* (`0.5 if is_concession else 1.0` in GDScript) — that is shorthand for selection, not a comparison.

**Watch:** `=` assigns, `==` compares. GDScript will refuse `if balance = 0.0:` — read the error, don't fight it.

## Check Your Understanding

1. In `if balance >= fare and is_concession:` — which two operator codes could you label, and on which symbols?

>| ### Answer
>| C624 on `>=` (conditional operator), C623 on `and` (logical operator).

2. Why will `if balance = 0.0:` not run?

>| ### Answer
>| `=` assigns; comparing needs `==`. Godot reports a parse error.

3. In `total_cards % 2 != 0` — what does `%` do, and which code is it?

>| ### Answer
>| `%` gives the remainder after division — C612 (arithmetic). The `!=` beside it is C624.