A box remembers one thing so you can use it later. Making a box is called grunk; changing one is a plain =.

grunk name = "Ugg"
grunk rocks = 3

oga name, "has", rocks, "rocks"

rocks = rocks + 1
oga "now", rocks

Making vs. changing

Why so strict? Because typos are the number one bug for new coders. If you write rock = rock + 1 but the box is called rocks, CMC tells you right away instead of quietly making a new box.

Boxes hold one thing

A box holds one value. You can put a text in it today and a number tomorrow, but the value it holds right now is the value you use:

grunk thing = "rock"
oga thing            ugg rock
thing = 5
oga thing + 1        ugg 6

Boxes live in the shape of your program

• Boxes made at the top level live for the whole program.
• Boxes made inside a clump are that clump's own private boxes. They

disappear when the clump finishes.

• A clump can read boxes from outside, but if it uses grunk on a name it

makes its own new box with that name.

grunk greeting = "hello"

clump say_it()
    grunk greeting = "BOOGA"    ugg this is a new, private box
    oga greeting
unga

say_it()                 ugg BOOGA
oga greeting             ugg hello (the outside box is untouched)

The magic boxes

You cannot use these names for boxes you make.

Good names

• rocks, total, player_name, is_awake
• Say what is inside, not what kind of thing it is.
• r is fine for a quick loop, but rock_count is better when you come back

tomorrow.

A tiny example

grunk apples = 3
grunk friends = 2

grunk each_gets = flat(apples / friends)
grunk leftover = apples % friends

oga "each friend gets", each_gets
oga "left over:", leftover

each friend gets 1
left over: 1

Next: Choices -- making the computer decide things.