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BRIAN: Hello, world.

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My name is Brian, and I'll be
your walk-through lead in CS50.

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For each problem, I'll go
through what's required,

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as well as giving you a high
level overview of how you might

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solve each of the course's problems.

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And I'll give you some
hints along the way.

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So let's begin with Hello.

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Inside of hello.c, right
now, we have this code,

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which is some code inside of a main
function that prints out "Hello, world"

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to the screen.

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How can you actually run this code?

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Well, if you go to your
terminal and run make_hello,

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this will compile your program.

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Once you've compiled your program,
you can run your program by running

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./hello, at which point you should
see the words "Hello, world"

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printed to the screen.

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Your task in Hello is to modify this
program to make it more interactive.

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What we're going to have your program
do instead is, when you run ./hello,

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the program should prompt by
asking, "What is your name?"

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The user will then type in their
name, like Brian, for example,

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and the program will say "Hello, Brian."

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So what do you have to do?

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You'll, first, want to prompt the user
for their name by asking for their name

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and letting them type
it in, and then, you'll

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want to say hello to that user, giving
their name in your printout statement.

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So how might you actually do that?

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Well, to get input
from the user, you can

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take advantage of the
get_string function, defined

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in the CS50 library in CS50.h.

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To use get_string, you'll write
get_string, and get_string

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takes an argument,
inside of parentheses,

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which will be the prompt,
what's displayed to the user

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before they have to type in
some_string, for example.

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So our prompt, in this
case, can be "What

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is your name," followed by
that backslash n character,

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which you might recall
represents a new line.

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This line needs to end
with a semicolon, and we

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want to take the result of get_string
and save it inside of a variable.

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And we're going to save it
inside of a variable called

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name whose type is string.

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So a line like this will prompt the
user by saying, "What is your name?"

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The user will type in their
name, and when they press Return,

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their name will be stored inside
of that variable called name.

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Once the user has typed in their
name, the next thing we need to do

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is actually say "Hello" to that user.

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How might we do that?

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Well, we already have
code that says "Hello,

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world," that looks something
like this, printf prints

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out some string to the
terminal screen, and the string

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"Hello, world" is what
ultimately gets printed.

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But instead of printing
"Hello, world," we instead

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want to print "Hello, Brian,"
for example, or "Hello"

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to whatever user's name
was actually typed in.

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So what we might do here,
instead, is use a placeholder.

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Here, instead of "Hello, world,"
we're saying "Hello, %s,"

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where %s is a place holder for a string,
meaning we're going to plug in some

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string into this point of the string.

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Now, what string are
we going to plug in?

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We're going to plug
in the string "name,"

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so we provide the variable "name"
as an additional argument to printf.

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This whole line, now, is
going to say "Hello comma"

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and then plugging in whatever the value
of the string "name" happens to be.

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Once you do that, you should be able
to test your program by running it.

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First, compile it by running make_hello,
then after it's compiled, run ./hello,

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and then, that should prompt
you to type in your name.

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Type in your name, and then your
program should say "Hello" to you.

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My name is Brian, and this was Hello.

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