Ruby Programming Tutorial - 2 - Writing a Simple Program Video Lecture

alright guys welcome to your second Ruby
tutorial and before I start showing you
guys the Ruby code I want to talk to you
guys a little bit about computer
programs in general so just remember
that computers can't understand English
computers can only understand simple
instructions now in Ruby programming we
call these instructions commands so
basically whenever we write a ruby
program it's going to be made up of a
bunch of little commands in each command
is going to be on a separate line so
just remember that we can tell the
computer what to do by writing a bunch
of little commands or instructions and
whenever you put bunch of these commands
together we turn into basically a
computer program that's all a computer
program is a bunch of little commands
pretty much put together simple enough
so let me go ahead and show you guys a
very simple command we already looked at
one in the last tutorial which was like
seven plus four or something like that
but let me just show you guys a command
just so I can talk you guys through so I
know you guys don't know what any of
this stuff means yet but let's just go
ahead and type something real quick mmm
bacon just like that and and so
basically what I wrote is this seven
times do print mmm bacon end okay sounds
kind of weird well this is a sample or
an example rather of a very simple Ruby
command even though we can't understand
it it's a command that Ruby can
understand oh excuse me got some phlegm
in my throat so basically our language
is different than Ruby's language and
it's my job I guess to teach you Ruby's
language so another thing that I want to
point out before we continue along is
let's take a look at the interactive
Ruby environment this IRB just stands
for interactive Ruby and it's basically
just the program don't mind this main
for right now I'll talk about that later
on
now the 0:01 is just the line number the
very first command right is going to be
0 0 1 the next one is going to be on
line 0 0 2 if we were to write something
else
such is I know you guys don't know this
command either but like this one it
would be on zero zero to the next one
would be on zero zero three so on and so
forth
now after this you see an additional
number which is zero zero zero this
number is the depth and I'm gonna talk
about the depth later on when we begin
talking about classes and stuff like
that but for now on just concentrate
concentrate on the line number one two
three
each command you write is on a separate
line now while I'm talking about the
interactive ruby environment I guess I
might as well mention this because I
know a lot of you guys are like wow this
is pretty much the most boring looking
program ever if you want to change the
colors of this text then go ahead and
right-click it and choose properties and
if you go to font you can go ahead and
change the size of it colors you can go
ahead and change the text color and I'll
probably change these from tutorial 4 to
tutorial depending on you know whatever
mood I'm feeling but you can go ahead
and change all the colors here so now
with that being said like I said my job
is to teach you the basic commands
basically I want to teach you the
language that Ruby understands now
probably the most basic command in the
easiest to understand is just a print
statement go ahead and write print now
in between double quotation marks go
ahead and write anything like hello
people of YouTube now go ahead and hit
the enter button and whenever you hit
enter it basically takes what's ever in
between those quotation marks and it
prints it out on the screen in this case
hello people of YouTube now what no
means is you say ok it printed that out
good job Ruby but it also has this
little equals an arrow sign and it has
Nell what the heck is this
well don't worry about the equals arrows
right now I'll be talking about that
later on
but now I'll explain this Nell pretty
much means nothing
Nell and il equals nothing so why does
it say hello people of YouTube nothing
that doesn't make sense
they're basically it says no because you
have nothing or no heirs you didn't mess
up at all pretty much all your code was
typed perfectly like Ruby expected if
you do type a command or something that
Ruby doesn't understand for example just
go ahead and then slam your fingers
across the keyboard and type something
random now if we hit enter Ruby's not
gonna understand this command it doesn't
make sense it doesn't even make sense to
us
so go ahead and hit enter and we see
that we get an error message name error
undefined local variable so that's the
difference between a successful command
and an error
whenever you have a successful command
for example this print command is just
gonna go ahead and run that command and
return nil and whenever you have an
error or something it doesn't understand
an air typically looks like this it says
what type of error it is and then it
gives you some information about it so
basically that's the difference between
a successful command a very simple basic
command and an error so I just want to
tell you guys that give you guys a
little history of computer programs what
they're made up of basically I showed
you guys a simple print statement such
as print hello people of YouTube that's
a very basic command but there are a ton
of other commands that we need to know
for the Ruby programming language and
again if you ever have an error you're
gonna see something like this right here
so anyways in the next story I'm gonna
be talking about how to do some simple
math with Ruby as well as teaching guys
about something called variables and
it's going to be amazingly exciting so
anyways thank you guys for watching
don't forget subscribe and I'll see you
guys in the next video