Computer Use

Contains how-to guides for the command line, operating systems, filesystems, software installation and handling media formats.

Installing and Launching the Command Line on Your Computer

The command line -- sometimes also called the terminal or the shell -- is a way of navigating and using your computer that is similar to using the file browser (on mac: Finder, on Windows: File Explorer). It can be used to find, open and move files, run code, use version control software such as git, and install software.

The command line can be counter intuitive to use for the first time, and like many computer programming tools requires practice to be able to use fluently. It's also extremely useful, and presumed knowledge in software engineering jobs. The benefits of using the command line are many -- and you don't need to use it for everything to get good results.

Installing a Command Line

An important way to think about the command line is one way among many to navigate the computer. There are several different 'command lines' that you can have access to. For this guide, we will use Terminal for Mac users, and Git Bash for Windows users, which will allow us to use the same commands.

On a Mac

The most commonly used command line on Mac is called Terminal. This comes installed by default on all macs, so you don't need to do anything. Scroll down for the launching instructions.

On Windows

In this guide, we will give instructions for using a "Unix type" command line. This does not come installed by default on Windows systems, which instead have something called 'Command Prompt' -- commands used on Unix type command lines are different.

The command line we will install instead is called Git Bash.

Step 1: Download You need to download Git Bash by clicking the 'Windows' link on this website. This will take you to a page with multiple different options. To get the most recent installer, click the link circled in red below.

Step 2: Launch Installer Once your installer has downloaded, navigate to the 'Downloads' folder on your computer and double click the file called something like 'Git-2.49.0-64-bit.exe' (the numbers in yours might be different). This will open the installer.

Step 3: Click through Installer Click through each step, selecting the default options. When you reach the 'Select Components' option, make sure the following tools are selected.

Select Nano as the default editor. This is easier to use than Vim, which is set as the default. You can also select any other listed editor that you are comfortable with.

Leave everything else as default, and click through to the end!

Launching the Command Line

On a Mac

Step 1: To open the Terminal, press ⌘ and Space to open the 'Spotlight Search'. Type 'Terminal', and you should see a black icon with a white triangle.

Step 2: Press enter, and a window should open. Depending on your computer's settings, it will have either a white or a black background. It should say 'zsh' at the top, and have a ~ symbol, possibly combined with your username.

Step 3: Sometimes, the first time you open a Terminal on a Mac, it might come up with a message saying “The default interactive shell is now zsh.” -- this is fine and you don't need to do anything! This is just giving you some information about the software that runs the command line.

On Windows

Step 1: To open Git Bash, navigate to the Start menu and start to type 'Git Bash'. Click on the application to open a window.

Step 2: You should see a window open, probably green, pink, yellow and white text on a black background. This will have your computer's name followed by a ~ symbol, and a $ with a flashing cursor next to it.

Congratulations, you've got a command line!

Workshop: File Systems and the Command Line

In this workshop we will get to know our computer better, learn about the idea of the filesystem, and explore it using a tool called the Command Line. We will learn some useful commands, and also learn more about how computers work, which will prepare us for writing code. If you need a reference at any point in the workshop, there is a list of commands included at the end of the page.

To get set up for this workshop, you need to have a suitable Command Line that you can launch installed on your computer. Please follow the instructions in this guide to make sure you have this, especially if you use Windows.

The exercises in this workshop are heavily inspired by Melanie Hoff's Folder Poetry class, which Agnes attended many years ago, and is a great introduction to the computer.

Intro: What are Computers?

Computers are Everywhere!

We have access to a lot of different devices that run code and software. These include systems like a laptop or a desktop computer, but also phones, watches, cars, tablets and e-Readers. Some of these devices, like desktop computers, give us some control over how they operate, and allow us to look inside them. Others, like phones, hide a lot of their inner systems away and make it hard for the average user to look inside.

Your Computer is a Load of Files

Lots of things have changed about computers in the past few decades -- they're a lot faster, there is a lot of emphasis on graphics, and it's much easier to find things than it used to be -- but the way that computers work has not fundamentally changed. All computers use something called an 'operating system' to work: you might use an operating system like Mac or Windows, or maybe one of a family of systems called Linux.

These different operating systems will work on slightly different principles, but at the core there are lots of similarities.

What is a file? It's a way that your computer stores a load of information, grouped together in one place, and represented by a specific format. We will explore formats more next week.

Demo: Secret Files

We are going to look inside an application and see all the files that make it up. You are welcome to follow along -- but it's also fine to watch this part! In this demo, I will also show you how to make your file browser a better tool for seeing inside your computer. When I do these steps, have a go at doing them with me.

Activity: Command Line House Tour

In this part of the workshop, we will make an explorable game using the command line. By the end of this activity, you should be more familiar with your file browser

We will use generic names to refer to specific things. So:

Intro: the filesystem

The filesystem is the name given to the system on your computer that manages and looks after files. It's the part of your computer that you navigate in order to open, read and edit different files.

Part 1: Navigating using the File Browser

Step 1: Open
Open the file browser. on your computer. On a Mac, this is called Finder. On Windows, this is called 'File Explorer'

Step 2: Desktop
Click to navigate to the 'Desktop' in the file browser. The desktop is just another folder, but on both Mac and Windows, it behaves like a special folder where you can see the files on your main computer screen.

Step 3: Class Folder
We are going to make a folder to store all the files made in this workshop. In your Desktop, create a new folder called 'computer-friend'. Make sure you use a dash rather than a space! We'll find out later why this is important.

Part 2: Exploring the House

I've made a small game to demonstrate the activity. We're going to download and extract it, put it in our new folder, and then look inside.

Step 1: Download
Download the 'house-tour' folder by clicking on this link.

Step 2: Extract
This is a 'zipped' folder -- it is a way of compressing a bunch of files into a smaller, single object so it can be sent around. We need to extract the files

Step 3: Move
We are going to move the unzipped folder into the 'computer-friend' folder we made in part one. Open a second file browser window, then drag and drop the 'house' folder inside of the 'computer friend' folder. You should end up with a folder layout that looks like this (look at the path bar to see the structure):

Part 3: Navigating using the Command Line

Now we are familiar with our house, we are going to explore it again, but this time using the command line.

Step 1: Launch the Command Line
Open the command line on your computer. Use this guide as a reference if you're not sure how! If you use windows and you haven't done this already, make sure you follow the instructions in that guide to install and open Git Bash.

Step 2: Navigate to the House
When we downloaded the 'house' folder, we moved it to a folder on our Desktop that we navigated to by clicking. We are going to do the same thing now, but using text commands. When you click on your terminal window, you should see a shaded block indicating your cursor. If you start typing, text will appear there.

We are going to use the cd command to navigate. Type out the follwing line, and press enter. To make sure you learn it, type it manually rather than copy pasting!

Challenge: Find the secret room
There's a hidden room in the house! You can modify the ls command with ls -a to show hidden folders and files. Try to locate this secret room and solve the puzzle inside!

Part 4: Making folders and files using the Command Line

We are going to make an extension for the house! As an example, we are going to make an extra room called cellar, and then fill it with objects that people in the house have thrown away.

Step 1: Corridor
Navigate to the 'corridor' folder in the house, using the cd command. A simple way to do this is to type cd .. until you end up back at the folder house, and then use cd door/corridor to go back to the corridor. It's important we move to the correct location before we create our file there

Step 2: Making a Folder
We've already made a folder in our file browser. To do the same thing in our command line, we're going to a command called mkdir, which stands for 'Make Directory'. To use the command, type mkdir, then a space, then the name of the folder you want to make (without a space in it). Then press enter.

When you type in ls, you should see the new file.

Step 3: Making a File
To make some objects in the cellar, we need to go inside it. Use the cd command to navigate.

The command we use to make a new file is touch. This is a weird name, and refers to an old way of talking about how opening a file could affect computer memory. To create a text file, we will use it like this:

We can now open this file in a text editor.

Challenge: Add another room
Now you have a sense for how these commands work, try adding another room somewhere in the house, using the mkdir command! Try adding some objects using the touch command.

Extra tips
touch and mkdir can be used to make multiple things at once. So, if you type mkdir house garden street, it will make three folders in your current location: one called house, one called garden, one called street

Part 5: Make your Own Adventure

Step 1: space
Think of a space that you'd like to give someone a tour of. It could be real or imaginary, manmade or natural -- maybe it's your house, or a forest near where you grew up, or the top of a skyscraper

Step 2: make it a home
Navigate back to your 'computer-friend' folder in the command line, using the cd .. command. Now, use mkdir your-space-name (replace 'your-space-name' with the name of your space) to make it a folder. You can use the ls command, or the file browser, to check that it was made in the place you thought!

Step 3: add rooms and objects!
Navigate inside it using cd your-space-name (again replacing 'your-space-name' with whatever you called the folder.

Step 4: add rooms and objects!
Still using the command line, and the commands we learned above, try fleshing out your space by adding rooms, folders and objects. Consider using a piece of paper to make a map to help you plan! If you get lost, there's a cheatsheet of commands at the bottom of this page.

Try and make a space that contains at least 4 rooms, and 6 objects.

Part 6: Text Adventure Swap

Now, try and share your adventure with someone else in the class (if you're doing this at home alone then you can always send it to Agnes).

Step 1: Compress the Files
Using your file browser, navigate to the Desktop, where you should be able to see the 'computer-friend' folder.

Step 2: Share the Files
Using Slack or Email, share the files, either with the class or with the person next to you!

Tools and Further Reading

File Browser Commands

Show hidden files:

Show path bar:

List of Command Line Commands

In this session, we are going to use the following commands:

command name meaning
pwd "print working directory" print out a path to my current location
ls "list" list the files and folders in the current location
cd "change directory" move to a different folder
cd .. "change directory" move UP one folder
cd ~ "change directory" navigate to the Home directory
touch file.txt "touch" make a new, empty file called file.txt
cat file.txt "concatenate" print out the contents of a file called file.txt
mkdir my-folder "make directory" make a new folder called 'my-folder'
echo "some text" "echo" write out the text "some text"
echo "some text" > file.txt "write" overwrite the contents of file.txt with "some text"
echo "some text" >> file.txt "append" add the text "some text" to the end of file.txt

Neat tricks:

Watch out for:

Further Reading

If you would like to explore more of the ideas covered in the workshop, take a look at one or all of the following readings:

Workshop: Media Types and File Sharing

This workshop will cover different types of files and media. We will look at audio, video and image files, and how they are made, learn how to convert between them and how to find them online. We will use the command line to make tiny media libraries, and share them with one another!

Intro: file formats

At the most basic level, information on computers is represented by strings of ones and zeroes. The ones and zeroes are grouped together into 'files' (containers for information), and those files arrive in a 'format'. To differentiate the ones and zeroes that make up an image, from those that make up text, audio or video files, computers need a lot of structuring information. You can think of a 'file format' as a set of standardised rules for how the computer should read and display the information it finds in a file, and how it should structure that information for files that can be read in the same way.

^ an image displayed in 'hex code'

Many of the distinctions between different kinds of media file formats are based on mathematical differences about how information in them is compressed. For example, the difference between the audio formats .mp3, .wav and .ogg, or the image formats .jpg, .png and .bmp are mostly to do with how much space they take up on a computer. There are also political and legal differences -- for example, the differences between the the Microsoft Word Binary File Format (.doc), the Open Document Format (.odt), and the Open Office XML format (.docx) are that the first file format belongs to Microsoft, the second was explicitly intended to be an open standard, and the third became the standard interchange with heavy influence from Microsoft.

^ A protest in Bangalore, India, against the ECMA's adoption of the .docx standard. The banner in the background reads "Liberate Your Documents"

File formats are not naturally occurring phenomena -- there are large bureaucratic bodies dedicated to the design, development and standardisation of different file formats. Historically, there have been huge debates about file formats -- particularly around questions of proprietary file formats and licensing.

Recognising file formats

File names give you core information about the files themselves. The part you are interested in is the end, or extension. Normally the letters and numbers in a file's extension relate to a longer sequence of words that describe the process of formatting that file -- so ".pdf" stands for "portable document format", and ".jpeg" stands for "joint photographic experts group", the name of the organisation who came up with the standard for JPEG formatting.

Plain text file formats

A file is referred to as "plain text" if it can be represented just as characters (letters, numbers, punctuation, symbols), and not its graphical representation.

Not all files which are about text are 'plain text' files! Word documents (.docx),

Binary file formats

A 'binary' file is any non-text file. To view the file in the way it was intended to be displayed, it would need to be opened in software that is designed to read that kind of file.

For example, to view a .jpg file, one needs to open it in an image viewer, a web browser, or another type of software designed to open images.

However -- all binary files, just like all text files, are still composed of strings of binary data. Unlike a text file, the characters that make up a binary file rarely form a good representation of the file's contents. This doesn't mean we can't still look at them!

Activity 1: Glitch a JPG

For the first activity, we are going to use a text editor. On a mac, the best text editor to use is TextEdit, and on Windows, is Notepad. Both of these should come installed by default.

Note: some more advanced text editors like Visual Studio Code will display images as images rather than as their text. This is probably useful if you're using images in a code project (like a website!) but not at all helpful for us today.

Step 1: Find a JPG file on your computer. If you can't find one, then feel free to use this example image of a Pallas' Cat from the Wikipedia page Pallas' Cat. Right click to save the file -- you can save it anywhere, but the easiest place to find it is your Downloads folder.

Step 2: Get some info about the file! One really helpful thing a computer can do is tell you loads of information about the files. On a Mac, the way to do this is to right click the file and select Get Info. On Windows, right click and select Properties. Look for a file that's between 800kB and 1.5MB. This will work with other files, but files in this range tend to work best!

Step 3: We will now open this file using a text editor. First of all, make a copy of the file if you'd like to keep it! Then, to open the copy:

On Mac:
This time, right click the file again and select open with, scroll to the end and click 'other'

When the selection of applications opens, navigate to the bottom and change the drop-down to All applications

In the list of applications, scroll down until you reach Textedit, and click to open the file. If it's greyed out, make sure you've completed the previous step.

You should see a text file full of characters appear!

On Windows
Right click on the file and choose "Open with" > "Choose another app". Scroll down and select Notepad. You should see a text file full of characters appear!

Step 4: Scroll through the file to get a sense of the shape of it. Avoid editing characters in the first section -- this often contains information about the file, rather than the contents, and can make the file no longer able to open.

Once you've scrolled down a way, try deleting a couple of characters -- save the text file, and see if any changes happen to the image. You will notice that information about the image tends to be organised in left-to-right rows -- edits earlier in the file will affect higher up rows. Here's a set of consecutive edits made to a JPEG as an example:

Demo 1: find and copy

This session will build on the command line commands from last weeks' session. If these are unfamiliar or you need more practice, a cheatsheet is available at the end of this page, and the full session is linked here.

1. find

The first command we will look at is the find command. Like the name suggests, this is used for finding things, and can be a useful and precise search tool.

Let's open up a command line and try and use it. First of all, I am going to navigate to the desktop using cd:

Next, I want to try and find a file. I'm looking for an image called "shrimp.jpg" -- I can use the find tool to search for it. Notice that it found it even though it's not in the same folder! That's because find searches subfolders of the folder you are in.

What if we just want to find jpg files? We can do that too, using the wildcard symbol *. * often stands in in computing for "anything you like". Here we use it to say, we want all the things that end in .jpg:

You'll notice that I had to specify I wanted to find by name! That's because find can be used to find all sorts of things. We can also try finding things that are larger than a certain size! Here's the command to list files bigger than 100MB -- notice the list is a lot shorter, and just includes things like screen recordings and photoshop files!

There's a good guide here to a list of common use cases for the command.

2. copy

The second command we're going to look at is the copy command. This is used for making a copy of a file in one location, and storing the duplicate in another. This can be really useful if we don't want to touch the original files!

Say I want to make a copy of some of the jpeg files from before in a new folder. First of all, let's list them! Maybe I only want ones less than 300kB in size:

The copy command takes the form: 
cp /path/to/a.txt /other/path

This means -- copy the file a.txt into the new location /other/path. In this case, I'm going to make a folder on my Desktop called lores-jpeg where I'm going to keep all these images.

In order to make sure the file paths are preserved, I'm going to wrap all the paths in quotation marks, or use the tab key:

Note that without much extra effort, we could make a tool that would do this for all these tools automatically. In this instance, we can use a bash script!

This is just for demo purposes to show you how these things can become useful: it's not within the scope of today's workshop to show you this in detail!

find . -name "*.jpg" -size -300k|while read i; do
  cp "$i" lores-jpeg/
done

this code runs the find command, reads it in line by line, and then runs the copy command on each line in turn!

Activity 2: Files Treasure Hunt

Using the find command, try and find at least one of each of the following types of file on your computer. Use the cp command to copy each of these files into one folder, with all the types in it. Don't use mv, because that will remove the files from their original location!

Example for finding jpg files:

$ mkdir my-file-storage
$ cd my-file-storage
$ find ~/Desktop -name *.jpg
$ cp ~/a/b.jpg ./

Challenge: rare format try and find as many file types as you can on your computer that don't appear on this list! See Wikipedia for a full list of file formats

Demo 2: move

The next command we will look at is mv, or move. One way to think about move is like copy, but the file is removed from its original location. We want to be a little more careful with this command, as we need to make sure we're still able to find the files that we are moving.

Like copy, move takes the following form:

mv path/to/file.txt new/path

This will move the file "file.txt" into the folder "new/path"

Let's try it on our jpgs -- I made a new folder called 'shrimps' and moved 'shrimp.jpg' inside of it.

A really common use of the move command is renaming things. Say we want to rename this image, which currently has a name (pic040-medium.jpg) to something more catchy.

I'm going to rename it like this:

Activity 3: Gallery/Mixtape

For the third activity, we are going to use the find, mv and cp commands to create a mixtape or gallery for someone. This can be anyone you like, they don't need to be in class! Your mixtape or gallery (or anthology if you like) should be a collection of files united by a theme, and arranged and named with some kind of intention. It's totally up to you what that is!

To do this, we will need to find some files. There are lots of places on the internet to find different kinds of media -- here are a few sources I like. Some are very broad, others are quite specific!

Writing a README

An important part of sharing files with other people is explaining what the files are for, what they contain, and how to read, use and open them. This is considered good practice in a lot of disciplines, but is particularly important when writing code, as the interaction of files can be complex. Within software development, there's a convention to title these files 'README' -- which functions as a command.

README files are always written in a plaintext format, so no special software is required to read them. Normally this is either a .txt ("text file") or .md ("markdown file").

Task: Write a short README file in txt format for your mixtape / gallery. Instruct the listener / viewer what software they should open the files in, and feel free to include artistic notes, thoughts, etc.

Tools and Further Reading

There's a nice list of common file formats here.

Reading

File Browser Commands

Show hidden files:

Show path bar:

List of Command Line Commands

In this session, we are going to use the following commands:

command name meaning
mv a.txt b/ "move" move the file "a.txt" into the folder "b"
mv a/ b/ "move" rename the folder called "a" to "b"
mv a.txt b.txt "move" rename the file "a.txt" to "b.txt"
cp a.txt b/ "copy" copy the file "a.txt" into the folder "b"
cp "~/Downloads/c.mp3" ./ "copy" copy the file "c.mp3" from "Downloads" into the current folder
find . -name "*.txt" "find" find all files ending in .txt inside the current folder

Commands we learned last week:

command name meaning
pwd "print working directory" print out a path to my current location
ls "list" list the files and folders in the current location
cd "change directory" move to a different folder
cd .. "change directory" move UP one folder
cd ~ "change directory" navigate to the Home directory
touch file.txt "touch" make a new, empty file called file.txt
cat file.txt "concatenate" print out the contents of a file called file.txt
mkdir my-folder "make directory" make a new folder called 'my-folder'
echo "some text" "echo" write out the text "some text"
echo "some text" > file.txt "write" overwrite the contents of file.txt with "some text"
echo "some text" >> file.txt "append" add the text "some text" to the end of file.txt

Neat tricks:

Watch out for: