What you will learn How to read a path, what a file extension actually promises, and the split between files people can read and files only machines can.
Folders sit inside folders. Written on one line, that nesting is a path.
| Piece | Meaning |
|---|---|
/ or C:\ | the outermost point — start here |
Users/jinho | your account's folder |
work | a folder inside it |
report.md | the file name and extension |
The separator differs by operating system. macOS and Linux use /, Windows
uses \. An example starting with /Users/… is a macOS one.
| Example | Meaning | |
|---|---|---|
| Absolute | /Users/jinho/work/report.md | the same place, called from anywhere |
| Relative | work/report.md · ./report.md | relative to the current folder |
| Up one | ../report.md | the folder above |
Give agents absolute paths. A relative path depends on "where you are right now", and that "now" can differ between you and the agent.
Registering a working folder is precisely the act of pinning that down.
The .md, .csv, .pdf at the end is the extension. It does not change the
contents — it is a label saying which program should open it.
Windows hides extensions by default. What looks like
report.pdfmay really bereport.pdf.exe. Turn extensions on in File Explorer — it is basic security hygiene.
This split keeps coming back later.
| Text files | Binary files | |
|---|---|---|
| Opened raw | readable | garbage characters |
| Examples | .txt .md .csv .json .py | .pdf .xlsx .hwp .png .zip |
| Change history | visible line by line | a wholly different file |
| For AI | feed it directly | needs an extraction step |
That last row is the practical one. It is why "conversion" appears whenever an agent handles a PDF or a Hangul document — picked up in Turning documents into material and Shapes of data.
Agents produce files; people look for them later. Names bridge the two.
A name starting with a dot (.env, .gitignore) is not shown by default.
Configuration files use this convention, so half of "there is no such file" is
a file that is simply hidden.
.envdeserves special care. It holds passwords and keys, it is hidden by convention, and sharing it by accident is an incident on its own — see Accounts, passwords, API keys, permissions.
It is about characters, not megabytes. A model sees a limited amount at once (the context window), so long documents are split and only the relevant part is passed. A 10MB photo costs far less than 1MB of text.
Because a path is an address. A registered absolute path does not follow the folder. If you move it, update the registration.
1. When is an absolute path safer than a relative one?
When "the current folder" may differ between parties — telling an agent where a file is, for example.
2. Does renaming .csv to .xlsx produce an Excel file?
No. The extension only says which program should open it. The contents stay CSV and the file opens broken.
3. Which is easier to hand straight to an AI — text or binary?
Text. Binaries (PDF, Excel, Hangul documents) need a conversion step to pull the characters out first.
Next, the window where you handle those files directly → The terminal and commands
HyperTeamsmacOS · Linux /Users/jinho/work/report.mdWindows C:\Users\jinho\work\report.md✗ renaming report.csv to report.xlsx makes it an Excel file✓ only the label changes — the contents are still CSV, so it opens broken✗ final.md · final_really_final.md · report (1).md✓ 2026-08-19-weekly-report.md · q3-returns-analysis.csv□ Hyphens over spaces — spaces need quoting on the command line□ Dates as 2026-08-19 — alphabetical order becomes chronological order□ Non-ASCII names work, but can break when uploaded to other systems