<a id="ch-17"></a>

## Chapter 17 — One laptop, and the version token stays in the lab

<!-- open-cyber-academy:lesson-figures:start ch-17 -->
### Lesson map

Lesson 17. Map, example, EX063.

```mermaid
flowchart TD
  A["Match is not a safety proof"] --> B["Install on one laptop first"]
  B --> C{"Does v2.1 leave the laboratory string?"}
  C -->|No| D["Keep one laptop and the lab token"]
  C -->|Yes| E["The summary has no version"]
```

The trial is one machine. The version characters belong to the synthetic bytes.

### Logical drawing

```text
staff summary
    matched download
    install on one laptop first
    no version number
laboratory bytes
    contain "catalogue-tool v2.1"
    synthetic installer
other staff laptop
    does not receive the tool in this file
```
<!-- open-cyber-academy:lesson-figures:end ch-17 -->

### Learning outcomes

After this chapter, you should be able to:

1. Keep the install on one laptop.
2. Keep `v2.1` inside the laboratory string.
3. Leave the second laptop without the tool.

### 17.1 A cautious install does not spread, and a laboratory token does not become a version line.

The staff summary says the catalogue download matched and that the tool is installed only on one laptop first, because a match does not prove the software is safe or free of bugs. The library has two staff laptops. The file never says the second one received the tool. Inside `lab_checkfile.py` the synthetic bytes include the characters `catalogue-tool v2.1`. That string is the laboratory input, fifty copies of it, not a version written on the staff page. The five-sentence summary records no version. A classmate who writes "v2.1 installed on both laptops" has moved a laboratory token onto a machine the summary left alone, and then onto a second machine. Leo keeps the trial at one laptop and leaves `v2.1` in the script.

### 17.2 Worked example

| What someone cites | What the file holds | Decision |
|---|---|---|
| Install on one laptop first | The summary | Keep one |
| Two staff laptops | The inventory | The second stays without the tool |
| `catalogue-tool v2.1` | Synthetic bytes | Leave it in the script |
| "v2.1 on both." | Not written | Refuse |

> **Synthetic case.** The second laptop is not given the catalogue tool.

### Errors and limits

One laptop is a limit on harm. It is not a certificate that the chosen laptop is safe.

### Apply

- **EX063 — Both laptops, version 2.1?** The summary installs the tool on one laptop first. The laboratory bytes contain `catalogue-tool v2.1`. May the note say version 2.1 is now on both staff laptops? *Rubric:* 3 = no; the install stays on one laptop; the second laptop does not receive it; `v2.1` stays inside the synthetic bytes; the summary records no version; do not edit `lab_checkfile.py`;; 2 = one laptop, and the token stays in the lab;; 1 = one limit;; 0 = none.

<!-- open-cyber-academy:chapter-navigation:start ch-17 -->
### Continue studying — lesson 17 (chapter 17 of 20)

[← Chapter 16](#ch-16) · [Course chapter index](../SUBJECTS.md) · [Chapter 18 →](#ch-18)

Continue to the next authored lesson.
<!-- open-cyber-academy:chapter-navigation:end -->

## Worked answers

<a id="answer-ex063"></a>
**EX063.** No. The install stays on one laptop, and the other staff laptop does not receive the tool. The characters `v2.1` stay inside the synthetic bytes. The summary has no version. Do not edit the script.