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DAVID MALAN: All right.

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This is CS50's Introduction
to Programming with Python.

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My name is David Malan and
this is an introduction

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to Visual Studio Code for CS50.

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Visual Studio Code, or VS
Code, is a very popular program

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nowadays for writing code.

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It's technically a text
editor, or nowadays really

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an IDE, an Integrated
Development Environment,

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which means it's a
program that's designed

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for enabling you efficiently
and effectively to write code

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in your computer.

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Now it turns out you typically
install VS Code on your own Mac or PC.

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It's free, open source
software, which means anyone

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can download it on their own computer.

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But typically, when installing
it on your own computer,

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particularly to use for programming
with a language like Python,

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there's a few other steps as well.

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You need to install
support for Python itself,

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you might need to configure some
of the lower level implementation

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details of your computer
just so that things work.

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And so instead, for this course, we
recommend that you use VS Code, yes,

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but you use it in the cloud by
way of CS50's own implementation

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thereof on top of something
called GitHub Code Spaces, which

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is a hosted version of the same.

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To use Visual Studio Code
for CS50, go to code.cs50.io

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where you'll be prompted to log in
with your free github.com account.

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After some number of
seconds or minutes, you'll

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then be redirected to your
so-called code space, which

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is your own virtual space in the cloud.

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Somewhere out there
on GitHub servers, you

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will have access to
your own storage space,

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really your own hard drive
in the cloud in which you

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can create files, run programs, and
even organize everything in folders.

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You'll also have the ability to write
code via that interface and much more.

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The interface you'll see
typically looks a little something

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like this, whereby you'll have at
the top left hand of your screen

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a File Explorer that allows you
to see all of the files you've

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created over time in your account.

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You'll then have the ability at
the top to actually write code

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by creating one or more tabs in
which to write your programs.

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And then perhaps less familiarly,
at the bottom of the screen,

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you're going to have access to
what's called a terminal window.

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A terminal window is a
command line interface,

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or CLI, which is very
much in contrast with what

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you and I are mostly
familiar with nowadays,

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which is a graphical
user interface, or GUI.

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Indeed, everything we're seeing
here is graphical by nature.

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There's buttons, and icons,
and windows, and more.

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But underneath the hood,
you actually have access

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not only to your own virtual hard
drive in the cloud, but actually

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your own server too.

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Somewhere out there on GitHub
servers is your own server

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in a sense, your own virtual
server, or technically called

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a container, in which all
of your own files will live.

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You then have the ability to create
files, run programs, even install

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additional software within
that server, or that container,

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because that server container is itself
running its own operating system.

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And the operating system
it's running is not

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Mac OS or Windows with which
you're probably familiar,

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but another popular operating
system called Linux.

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And Linux is used by so many
programmers and more nowadays

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not only to write code, but to run
it, on their own servers as well.

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So how can you go about leveraging
this new command line interface?

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Well, it's worth learning
just a few commands

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that you might not
have typed previously.

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These commands work not only
in Linux, but also on Mac OS,

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and also with some modification
potentially on Windows as well.

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But if you're using Visual Studio Code
for CS50 in the cloud at code.cs50.io,

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you'll have the ability to run
all these commands and more.

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And here is just a few of
those that you can type.

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I'm going to go ahead now and type code,
which actually is a command that comes

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with VS Code itself, that enables me
to create new files and open new tabs.

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I'm going to change screens
over to my own computer

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here in which I have full
screen VS Code for CS50.

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So this is my browser
window full screened

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connected to my own code space, my
virtual container, in the cloud.

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And suppose that I want to go ahead
and create my own first program

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called hello.py, a
program written in Python.

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In my terminal window, I could
type code hello.py and hit Enter.

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But before I do, notice at top
left in my so-called File Explorer,

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there's technically nothing there.

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There's some mention of code spaces
and some mention of my own unique ID.

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But there's no actual
files or folders there yet.

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But when I hit Enter, thereby
creating a new file called hello.py,

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I'm not only going to see it
appear in just a moment in a tab

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where I can edit it, I'm also going to
see a graphical representation of it

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up here, which is only to say that
this environment, this integrated

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environment, all works cohesively.

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Here we go.

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Hitting Enter.

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My tab has opened, my prompt is blinking
here, so I can start writing code.

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But you'll also see that
hello.py not only exists, but is

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highlighted as the file I've opened.

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Well, let me go ahead and write
a very simple program now.

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Print quote unquote in
parentheses, hello comma world,

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which as you'll see if
not already is perhaps

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the most formative,
most canonical program

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you can write first when writing
code in most any language.

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I'm going to go ahead now,
and in my terminal window,

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I'm going to run one
other command that you'll

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learn all the more about soon too.

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I'm going to run Python itself,
which is not only a language,

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it's actually a program that
understands that language.

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And if I specify not just Python
but a space, and the name of a file

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that I have created containing
code written in that language,

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crossing my fingers as always and hit
Enter, I've just run my own program.

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Now on our Macs and PCs, we're generally
in the habit of pointing and double

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clicking on icons or on our phones,
tapping on icons to launch some file

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or program.

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In a command line interface, or CLI,
everything is done with the keyboard.

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You can use your mouse to move
your cursor up and down as needed.

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But generally, you do
everything with your keyboard,

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not really with your mouse.

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Everything else on the
screen can be clicked on.

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But in your terminal
window, you'll generally

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see this prompt, a single
dollar sign that does not mean

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dollar or currency for that matter.

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It's just a standard symbol that
means type your commands here.

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And it's a visual indicator that
you can type your next command.

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And indeed, the two
commands I've thus typed

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are code to create my new
file within VS Code itself,

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and then Python, which we, CS50, already
pre-installed into your code space

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so that you have built in support from
day one with writing your own code.

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Now there's other things I
can do in this environment.

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I, for instance, could control
click, or right click up here,

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and see a whole menu of options
with which to edit, or modify,

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that file, just on Mac OS or Windows.

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I could click on some of these
icons at top left, the plus icon

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to create a new file or a new folder.

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So all of those GUI conventions,
Graphical User Interface conventions,

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are still there.

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But you will and should get more
comfortable over time with the command

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line interface alone, which does all
of those things and more for you.

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In fact, here are just a few more of the
commands that you can use within Linux,

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and this command line
interface specifically.

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We'll see in a moment LS, which
allows you to list all of the files

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in your current folder, CP, which will
allow you to copy a file from one place

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to another, MV, which will
allow you to move a file

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or really rename it from one
name to another, RM for remove,

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which will allow you to delete a file,
dir, sir, MKDIR, which will allow you

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to make a directory, that is a folder,
CD, which will allow you to change

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directories from one
folder to another, rmdir,

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which will allow you to remove
a directory, and then clear,

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which will just aesthetically clear
your terminal window, if like me,

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you like to keep things
a little bit tidy.

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Now these are just some
of the commands you can

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type within Linux at this command line.

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But they're really equivalent to all
the kinds of things you and I already

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do frequently on our own Macs or PCs.

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Let me go back to VS Code here.

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And let's just try out
a few of these here.

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I'm going to go ahead
and first clear my screen

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as though we're starting from scratch.

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But this doesn't change
or delete any of my files.

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It just clears my terminal window.

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I can alternatively hit
Control L to do the exact same.

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Now I'm going to go ahead and type LS.

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But before I hit Enter, note
that LS kind of sounds like list.

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And indeed, this command and almost all
of those others were fairly succinct

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in that LS means list, but you only
type the L and the S, no L-I-S-T.

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And this is true of a lot of
command line interface commands,

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just to enable you and I to
type things more quickly,

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a lot of these commands have this
very succinct syntax in names.

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So here we go.

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I've typed out LS already.

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I'm going to go ahead and hit Enter.

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And you'll see only one
thing, hello.py, which

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is to say when I try to list all of
the files in my current default folder

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that just automatically opens when
I launch VS Code in the cloud,

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I only see the one file exists, which
I can also see graphically here.

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Well, let me go ahead now
and do something else.

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Let's make a copy of
this file and call it,

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goodbye.py just so in anticipation
of writing a second program that says

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goodbye, world instead of hello.

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I'm going to do CP for copy, then the
first name of the file, hello.py, then

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a space, and then the new name for
the new file, goodbye.py, Enter.

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And now notice nothing
really has happened.

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And that's generally a good thing.

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If you don't see an error message
down here, you've done well.

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But you do see graphically up
here that both files now exist.

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Now I could open goodbye.py
in a couple of ways.

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I could actually just go up here
and double click on goodbye.py

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to open it here.

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Or I can type the same command
as earlier, code of goodbye.py,

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and now I'll have a
second tab open here.

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And for parallelism, I
could change this word

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from hello to goodbye just
so I have a second program

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now that it is indeed
the second file as well.

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Now what if I decide that
I don't want this file?

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And I'm going to go ahead and close
it here and I want to rename it

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and change it to--

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from goodbye.py to farewell.py.

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Well, it still says goodbye.py up here.

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And if I type LS down here,
I'll see a list of two files now

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that are in that same folder.

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Let me do MV for move,
goodbye.py, and then something

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like farewell.py instead.

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Enter.

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And you'll see that it
changed up here at left.

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And if I type LS again, you'll see
that it changed down here as well.

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Well, you know what?

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Let's never mind with farewell.py.

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Let's go ahead and just
remove this I'll altogether.

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I could go up here and
single click on farewell.py

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in my File Explorer, control click, or
right click, and then select Delete.

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Or down here on my command line
interface, I could do this.

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I could do RM space farewell.

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And now notice if I'm a little tired
of typing out these long file names,

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Linux and command line interfaces
frequently support autocomplete.

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So instead of typing farewell,
I'm going to type FAR,

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which sounds like more
than enough characters

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to finish the rest of my thought.

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And I'm going to hit Tab on my keyboard.

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And it just finishes it for me without
having to manually type the same.

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I'm going to go ahead and hit Enter.

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And I'll see a somewhat cryptic message
now, as many of them admittedly are.

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It's not an error.

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It's just a prompt.

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Remove regular file quote
unquote, "farewell.py".

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This is just a safety check to make sure
that I'm OK with deleting this file.

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Generally when prompted
with a question like this,

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go ahead and type in Y
for yes, or N for no.

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And hit Enter.

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And now nothing bad seems to have
happened in terms of any messages.

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But indeed, farewell.py is now gone.

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Well, what more can we now do?

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Let me clear up the screen
just for aesthetics sake here.

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And let's create one or more
folders, not just files.

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Let me go ahead and make a
directory here with MKdir.

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00:11:38,290 --> 00:11:41,890
And let me just call it folder, though
I could call it anything I want.

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Alternatively, I could go
up here to my File Explorer,

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click on the plus icon
here on the folder,

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and manually create a no folder as well.

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00:11:49,670 --> 00:11:53,960
But here again, the goal is to focus
on this command line interface instead.

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All right.

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00:11:54,460 --> 00:11:56,890
MKdir folder and hit Enter.

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00:11:56,890 --> 00:11:59,450
Nothing seems to happen in
the way of error messages.

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00:11:59,450 --> 00:12:01,540
But now, notice there's
not just hello.py,

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00:12:01,540 --> 00:12:04,810
but a folder, or
directory, called folder.

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00:12:04,810 --> 00:12:06,890
Well, what now can I do with that?

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00:12:06,890 --> 00:12:08,890
Well, let me go ahead
and see what's inside.

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00:12:08,890 --> 00:12:11,237
Well, in my GUI, my
Graphical User Interface,

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00:12:11,237 --> 00:12:14,320
I could click on the folder here in
this little triangle, and look inside.

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00:12:14,320 --> 00:12:17,362
And of course, there's nothing there
because I literally just created it.

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00:12:17,362 --> 00:12:19,600
But let me do this now
in my terminal window.

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00:12:19,600 --> 00:12:21,910
Let me type LS after clicking down here.

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00:12:21,910 --> 00:12:25,840
And we'll see both my folder, which
by convention has a slash at the end

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00:12:25,840 --> 00:12:28,510
to make visually clear that
it's a folder, not a file,

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00:12:28,510 --> 00:12:30,070
and there's hello.py.

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00:12:30,070 --> 00:12:32,320
Let me go ahead now
and change directory.

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00:12:32,320 --> 00:12:35,200
Now in Mac OS or Windows, we would
again just click or double click

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on the folder and see what's inside.

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00:12:36,940 --> 00:12:39,640
In a command line interface,
you need to be more deliberate.

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CD space folder, with or without the
slash is fine, and then hit Enter.

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And now you'll see that
your prompt changed.

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There's still a dollar sign.

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00:12:48,880 --> 00:12:51,430
But by convention, and
this is CS50 detail,

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00:12:51,430 --> 00:12:53,560
though other people do
this too in the world,

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00:12:53,560 --> 00:12:57,490
we have prefixed your prompt
with a just quick reminder

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00:12:57,490 --> 00:13:01,060
of what folder you're in so that
you don't forget whether you're

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00:13:01,060 --> 00:13:05,080
in your main folder where you just
began, or some other folder therein.

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00:13:05,080 --> 00:13:08,410
I'm going to go ahead now and type LS
to list the contents of this folder.

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00:13:08,410 --> 00:13:12,070
And of course, there's nothing there
because I haven't created any files.

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00:13:12,070 --> 00:13:17,240
But if I do this, I could do code of
farewell.py again to bring it back.

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00:13:17,240 --> 00:13:19,660
But this time in this
folder, hitting Enter,

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00:13:19,660 --> 00:13:22,840
you'll see a new tab opens here
where I can write some more code.

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00:13:22,840 --> 00:13:26,380
But you'll also see hierarchically
here, the farewell.py

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00:13:26,380 --> 00:13:29,210
is now inside of this folder.

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00:13:29,210 --> 00:13:32,330
Now suppose this is a mistake
and I didn't mean to do that.

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00:13:32,330 --> 00:13:33,190
What can I do?

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00:13:33,190 --> 00:13:36,220
Well, let me close the tab here,
even without writing any code.

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00:13:36,220 --> 00:13:39,280
And down in my terminal
window, let me do this.

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00:13:39,280 --> 00:13:43,480
I'm going to type LS to confirm
that, yep, farewell.py exists there.

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00:13:43,480 --> 00:13:47,500
But suppose I want to move
it into my main folder.

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00:13:47,500 --> 00:13:51,460
Well, like on Mac OS or Windows, I could
click on the file here, farewell.py,

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00:13:51,460 --> 00:13:54,320
and just kind of drag it up or
down to put it where I want.

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00:13:54,320 --> 00:13:56,500
But let's move it, not
rename it this time,

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00:13:56,500 --> 00:13:59,470
but move it using that
same MV command instead.

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00:13:59,470 --> 00:14:04,090
I want to move farewell.py
to the parent folder.

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00:14:04,090 --> 00:14:07,880
In the world of files and folders, you
can think of things like a family tree.

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00:14:07,880 --> 00:14:11,720
And if you want to go up hierarchically,
you want to go into the parent folder,

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00:14:11,720 --> 00:14:16,120
so to speak, whereas folder is
conversely a child of the default

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00:14:16,120 --> 00:14:18,080
folder in which we began.

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00:14:18,080 --> 00:14:20,380
So I want to move farewell higher up.

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00:14:20,380 --> 00:14:21,730
How do I express that?

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00:14:21,730 --> 00:14:24,280
Well, another piece of syntax
in a command line interface

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is typically this, dot, dot.

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00:14:26,560 --> 00:14:31,630
Dot, dot is a symbolic representation
of whatever the parent directory

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00:14:31,630 --> 00:14:33,520
is, no matter what its name is.

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00:14:33,520 --> 00:14:35,800
In this case, it's my
own default folder.

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00:14:35,800 --> 00:14:37,870
Doesn't even matter what
its name technically is.

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00:14:37,870 --> 00:14:39,220
It's not pictured on the screen.

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00:14:39,220 --> 00:14:40,720
I'm going to go ahead and hit Enter.

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00:14:40,720 --> 00:14:44,560
And watch what happens at top left
in the graphical version of the same.

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00:14:44,560 --> 00:14:48,100
We should see that farewell.py
now pops out of the folder

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00:14:48,100 --> 00:14:52,270
and the indentation changed to imply
that it's not inside of the folder now.

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00:14:52,270 --> 00:14:54,730
It's alongside hello.py.

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00:14:54,730 --> 00:14:58,060
Indeed, if I close the folder
here, I don't see a difference

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00:14:58,060 --> 00:15:00,220
because there's nothing
in there as well.

300
00:15:00,220 --> 00:15:02,890
Let me type LS to confirm
in my terminal window.

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00:15:02,890 --> 00:15:04,310
There's nothing in folder.

302
00:15:04,310 --> 00:15:06,070
Let me now go back to
my parent directory.

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00:15:06,070 --> 00:15:07,390
And I can do this in different ways.

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00:15:07,390 --> 00:15:09,098
And like with programming
itself, there's

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00:15:09,098 --> 00:15:12,950
going to be many ways sometimes that you
can navigate a command line interface.

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00:15:12,950 --> 00:15:13,750
Here's one.

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00:15:13,750 --> 00:15:17,650
I can do CD for change
directory, and then space dot,

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00:15:17,650 --> 00:15:20,140
dot to go back to the parent directory.

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00:15:20,140 --> 00:15:22,150
But another technique,
especially if you're

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00:15:22,150 --> 00:15:24,430
a little less comfortable
with this whole new world,

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00:15:24,430 --> 00:15:26,263
is whenever in doubt,
if you want to go back

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00:15:26,263 --> 00:15:29,770
to your default directory in which
you began when you logged in,

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00:15:29,770 --> 00:15:33,250
just type CD with nothing
after it and hit Enter.

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00:15:33,250 --> 00:15:37,120
And you'll be whisked away
back to the starting point.

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00:15:37,120 --> 00:15:41,800
Indeed, if I type LS now, I'll see
farewell.py, my folder if empty,

316
00:15:41,800 --> 00:15:44,145
and hello.py as well.

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00:15:44,145 --> 00:15:47,270
Now, I don't really need this folder
because there's nothing in it anymore.

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00:15:47,270 --> 00:15:48,687
So let's go ahead and delete that.

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00:15:48,687 --> 00:15:52,205
I could click on it with control click
or right click in the File Explorer.

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00:15:52,205 --> 00:15:54,580
And I could delete it manually
like in Mac OS or Windows.

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00:15:54,580 --> 00:15:59,530
Or I can use my newfound commands, rmdir
for remove directory, space folder,

322
00:15:59,530 --> 00:16:01,690
with or without the
slash, and hit Enter.

323
00:16:01,690 --> 00:16:03,940
And because it's empty,
I'm not even prompted.

324
00:16:03,940 --> 00:16:06,430
It just goes away quite cleanly.

325
00:16:06,430 --> 00:16:09,250
And a final technique that
you'll find quite helpful

326
00:16:09,250 --> 00:16:11,500
in the context of a
command line interface

327
00:16:11,500 --> 00:16:14,620
is that it tends to store your
whole history of commands.

328
00:16:14,620 --> 00:16:16,480
In fact, not just autocomplete.

329
00:16:16,480 --> 00:16:20,170
But if I hit up, and up,
and up, and up, you'll

330
00:16:20,170 --> 00:16:24,250
see my history of all previous
commands scrolling up on there

331
00:16:24,250 --> 00:16:27,798
on the screen, which is helpful if I
just want to execute one of them again.

332
00:16:27,798 --> 00:16:29,340
I don't need to manually type it out.

333
00:16:29,340 --> 00:16:32,670
I can scroll up and down and
find the one that I want.

334
00:16:32,670 --> 00:16:35,390
So this then is just the
scratching of the surface

335
00:16:35,390 --> 00:16:38,270
of a command line interface in
the context of Visual Studio

336
00:16:38,270 --> 00:16:39,260
Code in the cloud.

337
00:16:39,260 --> 00:16:43,610
Most of these commands would be the
same whether on your Mac or PC, at least

338
00:16:43,610 --> 00:16:48,080
if you're using a terminal window that's
connected to a computer running Linux,

339
00:16:48,080 --> 00:16:51,260
be it a container, or a virtual
machine, or an actual server somewhere

340
00:16:51,260 --> 00:16:51,980
in the cloud.

341
00:16:51,980 --> 00:16:57,260
In the weeks to come for this class,
will you have access to code.cs.cs50.io

342
00:16:57,260 --> 00:17:02,480
and in turn your own code space so that
you have access 24/7 365 via a browser

343
00:17:02,480 --> 00:17:04,550
alone so long as you
have internet access

344
00:17:04,550 --> 00:17:07,860
without needing to install
anything on your own Mac or PC.

345
00:17:07,860 --> 00:17:10,610
Toward the end of the semester,
if you're feeling more comfortable

346
00:17:10,610 --> 00:17:12,560
and would like to use
this same software,

347
00:17:12,560 --> 00:17:16,280
VS Code, if not Linux as well,
you'll be able to also install

348
00:17:16,280 --> 00:17:19,220
those for free on your own Mac
or PC and continue programming

349
00:17:19,220 --> 00:17:22,400
onward even after the courses own end.

350
00:17:22,400 --> 00:17:24,745
This then was Visual
Studio Code for CS50,

351
00:17:24,745 --> 00:17:27,050
and with it, a command line interface.

352
00:17:27,050 --> 00:17:30,339
And this is CS50 itself.

353
00:17:30,339 --> 00:17:32,170