The everyday computer, internet, safety and AI skills every tech and STEM job assumes you already have.

Digital Literacy for Tech & STEM Work

## Why it matters

Every career on this platform runs on computers: a data analyst's laptop, a lab's instrument PC, a PLC in a factory, a cloud server. When something is slow, crashes, or will not install, the people who fix it fastest are the ones who can picture what is going on inside the machine. You do not need to build a computer, but you do need a clear mental model of its parts.

## The core idea: input, processing, storage, output

A computer takes **input** (keys, clicks, sensor readings, network data), **processes** it, **stores** results, and produces **output** (a screen, a file, a signal to a motor). The physical parts that do this are the **hardware**. The instructions that tell the hardware what to do are the **software**.

### The main hardware parts

- **CPU (processor):** runs instructions, one tiny step at a time, billions of times per second. Modern CPUs have several *cores*, so they can work on several tasks at once.
- **RAM (memory):** fast, temporary workspace. Programs and the files you have open live here while you use them. RAM is wiped when the power goes off.
- **Storage (SSD or hard drive):** slower, permanent space for files and installed programs. It keeps data when the power is off.
- **GPU (graphics processor):** draws the screen and is also used for heavy parallel maths, such as 3D rendering and machine learning.
- **Motherboard:** the circuit board that connects everything.
- **Input/output devices:** keyboard, mouse, screen, USB ports, camera, and the network adapter (Wi-Fi or Ethernet).

A useful analogy: storage is your filing cabinet, RAM is your desk, and the CPU is you doing the work. A bigger desk (more RAM) lets you keep more things open without walking back to the cabinet.

### Software comes in layers

1. **Firmware** is built into the hardware and starts the machine (for example UEFI on a PC).
2. **The operating system (OS)**, such as Windows, macOS, Linux, Android, or iOS, loads next and manages everything.
3. **Applications** (a browser, a spreadsheet, a code editor) run on top of the OS.

## What the OS actually does

Applications almost never talk to the hardware directly. They ask the OS, and the OS handles:

- **Processes:** it decides which program gets the CPU and for how long, switching so fast that many programs seem to run at once.
- **Memory:** it gives each program its own area of RAM and stops programs from reading each other's memory.
- **Files:** it organises storage into files and folders through a *file system*.
- **Devices:** it uses *drivers* (small pieces of software) to talk to printers, cameras, graphics cards, and instruments.
- **Users and permissions:** it controls who can sign in and which files or settings each person may change.

## Worked example: opening a spreadsheet

You double-click `results.xlsx`.

1. The OS sees the `.xlsx` extension and looks up which application is registered to open it.
2. It loads that program from storage into RAM and creates a new *process* for it.
3. The program asks the OS to read `results.xlsx`. The OS finds the file on the SSD through the file system and copies it into the program's memory.
4. The CPU runs the program's instructions to work out what to draw, and the GPU puts it on the screen.
5. When you press save, the program asks the OS to write the changes back to storage.

If your laptop slows to a crawl with 40 browser tabs open, you can now explain why: RAM is full, so the OS starts moving data back and forth to the much slower storage.

## Check your own machine

Find out what you are working with:

- **Windows:** Settings > System > About shows the processor and installed RAM.
- **macOS:** Apple menu > About This Mac.
- **Linux:** in a terminal, run:

```bash
lscpu | head -n 15   # processor details
free -h              # memory in use and available
df -h                # storage space per drive
```

Sizes use **bytes**: 1 KB is about a thousand bytes, 1 MB about a million, 1 GB about a billion, 1 TB about a trillion. A typical laptop has 8-32 GB of RAM and 256 GB-2 TB of storage.

## Common mistakes

- **Confusing memory and storage.** "My laptop has 512 GB of memory" usually means storage. Memory (RAM) is the smaller, faster number.
- **Thinking the OS is just the desktop.** The wallpaper and icons are only the visible part. Most of the OS works in the background.
- **Ignoring updates.** OS updates fix security holes and driver bugs. Installing them promptly is one of the cheapest ways to stay safe.
- **Blaming hardware first.** Most "slow computer" problems are software: too many programs at start-up, a full disk, or a runaway process. Task Manager (Windows), Activity Monitor (macOS) or `top` (Linux) shows what is using the CPU and RAM.

## Quick recap

- Hardware is the physical machine: CPU, RAM, storage, GPU, motherboard, and devices.
- Software runs in layers: firmware, then the OS, then applications.
- The OS shares out the CPU and memory, manages files, drives devices, and enforces permissions.
- RAM is fast and temporary; storage is slower and permanent.

## Try it

Open the Do tab and take the quiz to check that you can name each part and what the OS does.


Name the main parts of a computer and learn what the operating system does for every program you run.

Hardware, software, and the OS

How Computers Work: Hardware and Software

Operating Systems: Crash Course Computer Science #18

Turn on file name extensions (Windows: File Explorer > View > Show > File name extensions; macOS: Finder > Settings > Advanced > Show all filename extensions).

In your Documents folder (or a synced cloud folder), create a folder named `coding-help-learning`.

Inside it, create the folders `notes`, `projects`, `downloads` and `archive`.

Create a plain text file named `README.md` in the top folder and write two lines: what the folder is for and today's date in YYYY-MM-DD format.

Find one file you downloaded recently, move it into `downloads`, and rename it with a date-first, lowercase, hyphenated name (keep its extension unchanged).

Look at the extensions of five files on your computer and write down which program opens each one.

Copy the full path of your `README.md` (Windows: Shift + right-click > Copy as path; macOS: right-click, hold Option, Copy as Pathname) and paste it at the bottom of the README.

Check that the folder is backed up: either it is inside a synced cloud folder, or you have copied it to a second place.

## Why it matters

A lab notebook export, a CAD drawing, a CSV of sensor readings, a Python script: technical work produces files, and lots of them. If you cannot find last Tuesday's results, or you send a colleague `final_v2_REAL.docx` instead of the right version, the work slows down and mistakes creep in. Good file habits are one of the easiest professional skills to learn, and people notice them.

## The core idea: a tree of folders

Storage is organised as a **tree**. At the top is a root (`C:\` on Windows, `/` on macOS and Linux). Folders (also called *directories*) contain files and other folders. The full address of a file is its **path**:

```text
Windows:      C:\Users\sam\Projects\bridge-survey\data\2026-10-14-strain.csv
macOS/Linux:  /Users/sam/Projects/bridge-survey/data/2026-10-14-strain.csv
```

Windows uses backslashes `\`, macOS and Linux use forward slashes `/`. Programs, scripts and the command line all find files by their path, so where a file lives matters.

## File names and extensions

The part after the last dot is the **extension**. It tells the OS (and you) what kind of data is inside and which program should open it. Turn extensions on so you can always see them: in Windows File Explorer choose View > Show > File name extensions; on macOS go to Finder > Settings > Advanced > Show all filename extensions.

Formats you will meet often:

| Extension | What it is | Opens with |
|---|---|---|
| `.txt`, `.md` | plain text, Markdown | any text editor |
| `.csv` | comma-separated table data | spreadsheets, Python, R |
| `.json` | structured data used by web APIs | text editor, code |
| `.xlsx`, `.docx`, `.pptx` | Office spreadsheet, document, slides | Excel/Word/PowerPoint, Google, LibreOffice |
| `.pdf` | fixed-layout document for sharing | browser, PDF reader |
| `.png`, `.jpg`, `.svg` | images (lossless, compressed photo, vector) | image viewer, browser |
| `.zip` | a compressed bundle of files | built into every OS |
| `.py`, `.js`, `.html`, `.sql` | source code | code editor |
| `.exe`, `.dmg`, `.msi` | programs and installers | run only if you trust the source |

**Plain text vs binary.** A `.csv` or `.py` file is plain text: open it in any editor and you can read it. A `.xlsx` or `.png` is binary: it only makes sense to the right program. Plain text formats are easier to share, compare and keep for years, which is why so much technical data uses them.

Renaming `report.pdf` to `report.docx` does **not** convert it. It only changes the label, and the file will fail to open. To convert, use "Save as" or "Export" in a program.

## Worked example: a project folder

Here is a simple layout that works for a course, a lab project or a small analysis:

```text
bridge-survey/
  README.md            what this project is, who owns it, how to use it
  data/
    raw/               original files, never edited
    processed/         cleaned copies made from raw
  docs/
    2026-10-14-site-visit-notes.md
  analysis/
    clean_strain.py
  output/
    2026-10-20-strain-summary.pdf
```

The rules behind it:

- **Keep raw data untouched.** Work on copies so you can always start again.
- **Date first, in ISO format** (`YYYY-MM-DD`). Files then sort in time order automatically.
- **No spaces or special characters.** Use lowercase words joined with hyphens or underscores: `site-visit-notes.md`, not `Site Visit Notes (new!!).md`. Command-line tools and scripts handle these names without trouble.
- **Describe the content, not the version.** Avoid `final`, `final2`, `latest`. Use dates, or proper version history (cloud documents and Git, later in this course and in Git & the Command Line).
- **A short README** tells future-you and teammates what is in the folder.

## Backups

Files are lost to dead drives, theft, accidental deletion and ransomware. A common rule of thumb is **3-2-1**: three copies of important data, on two different kinds of storage, with one copy off-site (for example a cloud service). At minimum, keep important work in a synced cloud folder or back it up to an external drive regularly. At work, follow your employer's storage rules: client or patient data often may only be stored in approved places.

## Common mistakes

- Saving everything to the Desktop or Downloads folder and never filing it.
- Hidden extensions, so `invoice.pdf.exe` looks like `invoice.pdf` (a classic malware trick).
- Editing the only copy of raw data.
- Spaces and symbols in names that break scripts later.
- Changing an extension to "convert" a file.

## Quick recap

- Files live in a tree of folders; a path is a file's full address.
- Extensions tell you the format. Turn them on.
- Use dated, lowercase, hyphenated names and a standard project layout with a README.
- Keep raw data read-only and back up with the 3-2-1 idea.

## Try it

Open the Do tab and set up a real project folder for this course.


Organise a project folder with clear names and recognise the file formats you will meet at work.

Files, folders, and file types

How to Organize Files and Folders in Windows for Beginners

Files & File Systems: Crash Course Computer Science #20

Open a text editor or a new blank document and type three short sentences about what you want to learn.

Select the second sentence using Shift + arrow keys, copy it with Ctrl/Cmd + C and paste it at the end with Ctrl/Cmd + V.

Cut the first sentence with Ctrl/Cmd + X and paste it at the bottom. Then undo twice with Ctrl/Cmd + Z and redo once.

Press Ctrl/Cmd + A to select everything, then Ctrl/Cmd + F to find one word. Save the file with Ctrl/Cmd + S into your `coding-help-learning/notes` folder.

In your browser, open a new tab with Ctrl/Cmd + T, jump to the address bar with Ctrl/Cmd + L, and search for 'keyboard shortcuts' plus the name of an app you use daily.

Close that tab with Ctrl/Cmd + W, then reopen it with Ctrl/Cmd + Shift + T.

Switch between the browser and your editor three times with Alt + Tab (Windows/Linux) or Cmd + Tab (Mac).

Take a screenshot of part of the screen (Windows + Shift + S, or Cmd + Shift + 4) and paste or save it.

Write the ten shortcuts on a sticky note or in your notes file and use them for one week.

## Why it matters

Technical work involves a lot of moving text around: copying an error message into a search, pasting a value into a spreadsheet, finding one word in a long log file, switching between documentation and your editor. Doing each of these with the mouse takes a few seconds. Doing them with the keyboard takes a fraction of a second, and it adds up to hours over a month. Shortcuts also keep your focus on the task instead of hunting through menus.

## The core idea: one modifier key, many apps

Most shortcuts are a **modifier key** held down plus a letter. On Windows and Linux the main modifier is **Ctrl**. On macOS it is **Cmd** (the command key). Most shortcuts are the same letter on every system, so learning them once pays off in browsers, editors, spreadsheets and email.

In this lesson, `Ctrl/Cmd + C` means Ctrl + C on Windows/Linux and Cmd + C on a Mac.

## The ten core shortcuts

| Shortcut | What it does | Memory hook |
|---|---|---|
| `Ctrl/Cmd + C` | Copy the selection | **C**opy |
| `Ctrl/Cmd + X` | Cut the selection | X looks like scissors |
| `Ctrl/Cmd + V` | Paste | next to C on the keyboard |
| `Ctrl/Cmd + Z` | Undo | the "oops" key |
| `Ctrl + Y` (Windows) or `Cmd + Shift + Z` (Mac, and many Windows apps) | Redo | undo the undo |
| `Ctrl/Cmd + A` | Select all | **A**ll |
| `Ctrl/Cmd + F` | Find on the page or in the file | **F**ind |
| `Ctrl/Cmd + S` | Save | **S**ave |
| `Ctrl/Cmd + T`, `Ctrl/Cmd + W` | New browser tab, close tab | **T**ab, **W**indow |
| `Alt + Tab` (Windows/Linux) or `Cmd + Tab` (Mac) | Switch between apps | hold Alt/Cmd, tap Tab to move |

Three more that are worth learning next:

- `Ctrl/Cmd + Shift + T` reopens the browser tab you just closed.
- `Ctrl/Cmd + L` jumps to the address bar so you can type a URL or search.
- Screenshot of part of the screen: `Windows + Shift + S` on Windows, `Cmd + Shift + 4` on a Mac.

## Text editing without the mouse

These work in nearly every text box, document and code editor:

- **Arrow keys** move one character or line.
- **Ctrl + arrow** (Windows/Linux) or **Option + arrow** (Mac) jumps a whole word.
- **Home / End** (Windows/Linux) or **Cmd + left/right arrow** (Mac) jumps to the start or end of the line.
- Add **Shift** to any of these to *select* as you move. For example, `Ctrl + Shift + right arrow` selects one word at a time.

## Worked example: reporting an error

A script fails and shows a long error. You want to search for it and paste it into a message to your team lead.

1. Click into the error output, press `Ctrl/Cmd + A` to select it (or `Shift + arrows` to select just the last line).
2. `Ctrl/Cmd + C` to copy.
3. `Ctrl/Cmd + T` for a new tab, then `Ctrl/Cmd + V` and Enter to search for it.
4. `Alt/Cmd + Tab` back to your chat app, `Ctrl/Cmd + V` to paste.
5. Made a mess of the message? `Ctrl/Cmd + Z`.

That whole sequence takes about five seconds once the keys are in your fingers.

## Finding the shortcuts in any app

You do not need to memorise every shortcut in every program. Two habits help:

- **Read the menus.** Most menu items show their shortcut on the right. When you use a menu item twice, note its shortcut.
- **Look for the shortcut list.** Many apps show one with `Ctrl/Cmd + /` (for example Google Docs and many web apps) or `?` (Gmail, GitHub). Code editors such as VS Code have a command palette (`Ctrl/Cmd + Shift + P`) that shows shortcuts next to each command.

## Touch typing

Shortcuts are faster still if you can type without looking at the keyboard. Touch typing means resting your fingers on the home row (`ASDF` and `JKL;`, with small bumps on F and J) and letting each finger cover its own keys. Free practice sites exist; ten minutes a day for a few weeks makes a noticeable difference. Accuracy first, then speed.

## Common mistakes

- **Pasting formatting you did not want.** `Ctrl/Cmd + Shift + V` pastes as plain text in many apps (on a Mac some apps use `Cmd + Option + Shift + V`).
- **Cut instead of copy.** If you cut and then copy something else before pasting, the first item is gone. Prefer copy, then delete.
- **Forgetting to save.** Desktop apps often do not autosave. Press `Ctrl/Cmd + S` whenever you pause.
- **Closing the wrong tab.** `Ctrl/Cmd + Shift + T` brings it back.

## Quick recap

- Ctrl (Windows/Linux) and Cmd (Mac) plus a letter covers most shortcuts.
- Copy, cut, paste, undo, redo, select all, find, save, tabs and app switching are the core ten.
- Add Shift to movement keys to select text.
- Menus and shortcut lists teach you the rest; touch typing makes it all faster.

## Try it

Open the Do tab for a short drill that uses all ten shortcuts.


Learn ten core keyboard shortcuts that work across almost every app and save you time every day.

Keyboard and productivity shortcuts

Tech Savvy Tips and Tricks: Keyboard Shortcuts

Hardware, the operating system, files and folders, and the keyboard shortcuts that speed up every task.