Added variable "r" that calculates the area

Checkpoint 1:
- A value corresponds to something defined/fixed.
In comparison, a name refers to something that can
vary or be manipulated in some sort of way
In real life, one example is SSN. Everyone has a
distinct SSN (value). A person can move from their
hometown (name) where they received their SSN but
SSN will remain the same for all their lives.

-It's helpful to use variable in programming
because it allows us to use a value in different
contexts/calculations. It also makes it easier
for the author and the readers to understand
what the numbers represent if they are named as
variables.

Checkpoint 2:
-Function is more nested and can have different
elements within, such as a value or a variable or
another function. It is similar to a variable
in a way that it can correspond to a certain value
when executed.
-Along the similar lines as the answer above,
functions can help organizing our codes by chunking
our calculations. I recall creating a lot of
functions for my physics lab data analyses because
it involved multiple dimensions of calculations with
massive amounts of data. Labeling each (or a
certain chunk of) calculation(s) greatly helped me
keep track of my analyses.

greetings.py

@@ -2,6 +2,6 @@
 # ------------
 # By MWC contributors
 
-my_name ="Chris"
+my_name = input("What is your name?")
 greeting = "Hello, " + my_name
 print(greeting)