Unplugged - Variables in Envelopes

This lesson is called variables in envelopes.

We're going to learn how we can build sentences when we're still missing pieces of information.

Most of us are already familiar with the idea of filling in a blank.

We do it when we're
putting our name on our homework.

Sometimes, there's more than one blank that needs to be filled out, and in that case,

we give the blank a label so that we know which piece
of information goes where.

Variables are placeholders for pieces of information that can change.

By using a variable for the missing information, we can continue working on whatever we were doing,

and let someone else fill in information later.

In software, we use variables a lot.

We use variables as placeholders for name, email address, and even username.

That way, we can let the program know where those details will appear

after the user fills them in.

We use variables all the time in our work.

Any time you need to store a piece of information
for later, we use a variable. Let's say we

Let's say we need to count the number of times the user has tweeted.

Every time that user tweets, we'll add one to that number.

And every time
the user deletes a tweet, we'll decrease that number by one.

Anytime we need to know how
many times that user has tweeted,

we'll just look at that variable.