Learn to Program with Small Basic

Try changing the value in karenBears and running the program again
to see what happens. Neat, huh? Changing the value of karenBears will also
change the value of lindaBears. Variables can make your programming life
so much easier!
Let’s check out some other important concepts you need to know for
when you want to use your own variables.
Assigning Expressions to Variables
Arithmetic expressions are combinations of variables, operators, and numbers.
They can be constant numbers (such as 3, 6.8, or –10), arithmetic operations
(such as 3 + 6 or 10 / 3), or algebraic expressions (karenBears / 2). Evaluating
an arithmetic expression in Small Basic is just like evaluating an expression
in math. For example, the expression 4 * 3 + 6 / 2 is evaluated as (4 × 3 + 6
÷ 2) = 12 + 3 = 15. You can also use parentheses in expressions to decide the
order of operations.
You can set variables to the result of an arithmetic expression using
an assignment statement. Your program grabs the value to the right of the
equal sign and assigns that value to the variable on the left of the equal
sign. You already did this in Listing 4-1; let’s build on that knowledge and
write some more variables set to arithmetic expressions!
Here’s an example:
barbies = 5
' You have 5 Barbies
ponies = barbies + 7
' You have 7 more My Little Ponies than Barbies
donate = (barbies * ponies) / 10 ' Total toys you need to donate
When you run this program, the variables barbies, ponies, and donate are
5, 12, and 6, respectively. Time to donate 6 toys!
You need to set the variable on the left of an assignment operator,
as you’ve seen in every assignment example so far. So this statement is
incorrect:
5 = barbies ' This is backwards, like the Twilight Zone
Try running it yourself to see if you get an error!
Passing Variables to Methods
A method’s arguments can be constants, variables, or even expressions. For
example, the argument to WriteLine() in the following statement is an arithmetic
expression:
TextWindow.WriteLine((3 * x + y) / (x - y))
If x = 7 and y = 5, this statement displays 13 on the screen. See if you
can figure out how to write and run this code. Remember to set x and y
first!
Using Variables 45