text stringlengths 1 81 | start float64 0 10.1k | duration float64 0 24.9 |
|---|---|---|
And as you might
imagine intuitively, you | 1,489.07 | 2.205 |
could sort of control click
or right click on this. | 1,491.275 | 2.125 |
And this little menu pops up. | 1,493.4 | 1.19 |
You can download the file, run
it, preview it, refresh, rename, | 1,494.59 | 2.58 |
or what not. | 1,497.17 | 0.53 |
>> And I could just delete,
and it would go away. | 1,497.7 | 2.56 |
But let's do things with a command
line for now, so as to get comfortable | 1,500.26 | 5 |
with this, and do the following. | 1,505.26 | 1.75 |
I'm going to go ahead and remove
a.out by typing literally rma.out. | 1,507.01 | 5.335 |
It turns out, the command for
removing or deleting something, | 1,512.345 | 2.545 |
is not remove or delete. | 1,514.89 | 1.39 |
>> It's more succinctly RM, just to save
you some keystrokes, and hit Enter. | 1,516.28 | 4.98 |
Now we're going to be somewhat
cryptically remove regular file a.out. | 1,521.26 | 3.447 |
I don't really know what an
irregular file would be yet. | 1,524.707 | 2.333 |
But I do want to remove it. | 1,527.04 | 1.62 |
>> So I'm going to type y for yes. | 1,528.66 | 1.49 |
Or I could type it out, and hit Enter. | 1,530.15 | 1.79 |
And, again, nothing seems to happen. | 1,531.94 | 1.5 |
But that is, generally, a good thing. | 1,533.44 | 2.4 |
>> If I type LS this time,
what should I see? | 1,535.84 | 4.65 |
Hopefully, just hello and hello.c. | 1,540.49 | 4.44 |
Now, as an aside, you'll
notice this star, asterisk, | 1,544.93 | 2.356 |
that's at the end of my programs. | 1,547.286 | 1.374 |
And they're also showing up in green. | 1,548.66 | 1.541 |
That is just CS50 IDE's way
of cluing you into the fact | 1,550.201 | 3.769 |
that that's not source code. | 1,553.97 | 1.31 |
That's an executable, a runnable
program that you can actually run | 1,555.28 | 3.6 |
by doing dot slash, and then it's name. | 1,558.88 | 2.14 |
>> Now, let me go ahead and remove
this, rm hello, Enter, remove regular | 1,561.02 | 4.84 |
file hello, yes. | 1,565.86 | 2.15 |
And now if I type LS,
we're back to hello.c. | 1,568.01 | 3.17 |
Try not to delete your
actual source code. | 1,571.18 | 2.737 |
Even though there are features
built into CS50 IDE where | 1,573.917 | 2.333 |
you can go through your revision history
and rewind in time if you accidentally | 1,576.25 | 3.62 |
delete something, do be mindful
as per these prompts yes or no, | 1,579.87 | 3.79 |
of what you actually want to do. | 1,583.66 | 1.721 |
And if I go up to the top
left hand corner here, | 1,585.381 | 1.999 |
all that remains is hello.c. | 1,587.38 | 3.316 |
So there's bunches of
other commands that you | 1,590.696 | 1.874 |
can execute in the world of Linux,
one of which is, again, Make. | 1,592.57 | 4.98 |
And we're going to Make
my program now as follows. | 1,597.55 | 2.63 |
>> Instead of doing clang,
instead of doing clang-o, | 1,600.18 | 3.09 |
I'm going to simply
literally type, make hello. | 1,603.27 | 2.59 |
And now notice, I am
not typing make hello.c. | 1,605.86 | 3.77 |
I am typing make hello. | 1,609.63 | 1.28 |
>> And this program Make that
comes with CS50 IDE, and more | 1,610.91 | 3.93 |
generally with Linux,
is a program that's | 1,614.84 | 2.25 |
going to make a program called Hello. | 1,617.09 | 2.03 |
And it's going to assume, by convention,
that if this program can be made, | 1,619.12 | 4.56 |
it's going to be made from a source
code file ending in dot c, hello.c. | 1,623.68 | 5.35 |
>> So if I hit Enter now, notice that
the command that gets executed | 1,629.03 | 3.18 |
is actually even longer
before than before. | 1,632.21 | 2.13 |
And that's because we've
preconfigured CS50 IDE to have | 1,634.34 | 2.33 |
some additional features built in that
we don't need just yet, but soon will. | 1,636.67 | 3.208 |
But the key thing to realize
is now I have a Hello program. | 1,639.878 | 3.592 |
>> If I type LS again, I
have a hello program. | 1,643.47 | 3.61 |
And I can run it with
dot slash a.out, no, | 1,647.08 | 4.99 |
because the whole point of this
exercise was dot slash hello. | 1,652.07 | 3.52 |
And now I have my hello world program. | 1,655.59 | 2.499 |
So moving forward,
we're almost always just | 1,658.089 | 1.791 |
going to compile our programs
using the command Make. | 1,659.88 | 2.208 |
And then we're going to run them by
dot slash, and the program's name. | 1,662.088 | 3.212 |
But realize what Make is doing for
you, is it is itself not a compiler. | 1,665.3 | 4.31 |
It's just a convenience program
that knows how to trigger a compiler | 1,669.61 | 3.7 |
to run so that you yourself can use it. | 1,673.31 | 3.16 |
>> What other commands exist in
Linux, and in turn the CS50 IDE? | 1,676.47 | 3.75 |
We'll soon see that there's a
CD command, Change Directory. | 1,680.22 | 2.887 |
This allows you within
your command line interface | 1,683.107 | 2.083 |
to move forward, and back,
and open up different folders | 1,685.19 | 2.42 |
without using your mouse. | 1,687.61 | 1.25 |
>> LS we saw, which stands for list
the files in the current directory. | 1,688.86 | 3.61 |
Make Dir, you can
probably start to infer | 1,692.47 | 2.18 |
what these mean now-- make directory,
if you want to create a folder. | 1,694.65 | 3.5 |
RM for remove, RM Dir for
remove directory-- and these, | 1,698.15 | 3.12 |
again, are the command line
equivalents of what you | 1,701.27 | 2.89 |
could do in CS50 IDE with your mouse. | 1,704.16 | 2.785 |
But you'll soon find
that sometimes it's just | 1,706.945 | 1.875 |
a lot faster to do
things with a keyboard, | 1,708.82 | 1.79 |
and ultimately a lot more powerful. | 1,710.61 | 3.08 |
>> But it's hard to argue that
anything we've been doing so far | 1,713.69 | 2.75 |
is all that powerful, when all
we've been saying is, hello world. | 1,716.44 | 3.55 |
And, in fact, I hardcoded the
words hello world into my program. | 1,719.99 | 3.75 |
There is no dynamism yet. | 1,723.74 | 1.79 |
Scratch was an order of magnitude
more interesting last week. | 1,725.53 | 3.79 |
>> And so let's get there. | 1,729.32 | 1.9 |
Let's take a step toward that by
way of some of these functions. | 1,731.22 | 4.09 |
So not only does C come with printf,
and bunches of other functions | 1,735.31 | 4.16 |
some of which we'll see
over time, it doesn't | 1,739.47 | 2.38 |
make it all that easy right out
of the gate in getting user input. | 1,741.85 | 3.91 |
>> In fact, one of the weaknesses
of languages like C, | 1,745.76 | 2.38 |
and even Java and yet
others, is that it doesn't | 1,748.14 | 2 |
make it easy to just get things like
integers from users, or strings, words, | 1,750.14 | 5.72 |
and phrases, let alone things like
floating point values, or real numbers | 1,755.86 | 4.11 |
with decimal points, and really
long numbers, as we'll soon see. | 1,759.97 | 3.27 |
So this list of functions here, these
are like other Scratch puzzle pieces | 1,763.24 | 3.76 |
that we have pre-installed in CS50
IDE that we'll use for a few weeks | 1,767 | 4.09 |
as training wheels of sorts, and
eventually take them off, and look | 1,771.09 | 2.92 |
underneath the hood, perhaps, at
how these things are implemented. | 1,774.01 | 3.2 |
>> But to do this, let's
actually write a program. | 1,777.21 | 3.25 |
Let me go ahead now. | 1,780.46 | 1.31 |
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