piis global - it's not defined within the function and it's accessible in the whole program.
area- Note there are two variables of that name! One is global ant the other one is local inside the function
a- Note there are also two variables of that name. This was that catch: Writing
a = a + 3has no point. A value is assigned to the local variable
a, but the function ends right after that, and this
ais no longer available, it will never be used.
bis only local - it's an argument for the