Random Values
Introduced| English | Meaning |
|---|---|
| unpredictable/ʌnprɪˈdɪktəbl/ | unpredictable |
| random/ˈrændəm/ | Describing outcomes governed by chance rather than being individually predictable with certainty. |
| range/reɪndʒ/ | The set or interval of values permitted or covered in a particular context. |
| variability/ˌveərɪəˈbɪlɪti/ | variability |
| outputs/ˈaʊtpʊts/ | A result produced by a function, calculation, device or program. |
Unpredictable on purpose
- Some programs need to be unpredictable — games, tests, simulations.
- A program can generate a random 随机 value within a specified range 范围.
RANDOM(1, 6)might return any whole number from 1 to 6, each with an equal chance.- It is like a dice built into the program.
RANDOM(1, 6) returns:
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It picks a random value within the given range.
Variability
- Randomness introduces variability 可变性 into a program's behaviour.
- Two runs of the same program can then behave differently.
- That is exactly what makes a game feel fresh each time.
- Nothing in the code changed — only the random value did.
RANDOM(1, 6) returns each value from 1 to 6 about equally often
Same every run, or varies?
A random value makes output vary between runs; a fixed calculation gives the same output every time.
Randomness introduces ______ so two runs can behave differently.
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The same code can give different results each run.
roll ← RANDOM(1, 6) does what?
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The generated value is stored in the variable.
Store and use it
- You usually store a random value in a variable for later logic:
- $\text{roll} \leftarrow \text{RANDOM}(1, 6)$.
- Now
rollholds one dice value the rest of the program can use. - Random values let a program model unpredictable 不可预测 events, like a coin flip.
Getting 4, then 1, then 6 from three runs of a dice program shows the program has a bug.
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False. The random value differs each run, so different outputs are expected behaviour, not a bug.
A coin-flip program uses RANDOM(1, 2). The two possible outputs are:
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1 maps to heads, 2 to tails.
Random values let a program model unpredictable events like a dice roll.
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This makes programs feel more like the real world.
Different outputs each run
- Because of randomness, repeated runs can produce different outputs 输出.
- Running a dice program three times might give 4, then 1, then 6.
Coin flip. A program picks RANDOM(1, 2), treating 1 as "heads" and 2 as "tails". One run stores 1 → "heads"; the next stores 2 → "tails". Nothing in the code changed — only the random value differs, so the output differs. This is expected, not a bug.
A random value is picked within a range (RANDOM(1, 6)), adding variability so two runs can differ. Store it in a variable to use it, and it lets a program model unpredictable events. Different outputs across runs are expected, not a bug.