We'll be looking at a sample application while we discuss the first couple topics. Create a new folder on your floppy disk and download the following files there to follow along:
A new one, similar to Integer...
Globals are usable everywhere---in every procedure.
Locals are only usable in the procedure in which they are
declared. As soon as the procedure's done, the variable
disappears.
Note correspondence between formal and actual parameters.
The key is recognizing that it'd be a good idea to design your program
to include a procedure or two. Before we start developing, we'll
discuss this. It's always a good idea to have a solid plan
before you do any work on the computer.
variables: storing data
Think of it like the Memory button on your calculator.vocabulary
types: What kind of data do you want to store?
So far, we've seen two:
declaration syntax
You can place declarations inside or outside procedures. More on this
in a second when we talk about scope.
Dim variable_name As type
Dim name_1 As type_1, name_2 As type_2, .., name_n As type_n
assignment syntax
Assignments can only be in procedures (Subs and Functions).
variable_name = expression
scope: the variable's "neighborhood"
The scope of a variable is the section or sections of code
where it can be useda, i.e. assigned and read.global vs. local
The key is where the variable is declared.
Unless you really need a variable in more than one procedure, it's a
good idea to stick with locals.
procedures (Subs): Do one job and do it well.
vocabulary
What's a procedure, really?
Why do we use them?
definition syntax
Sub procedure_name(formal_parameter As type, ..)
statement
..
End Sub
call syntax
Make sure: right number of parameters, right order.
Call procedure_name(actual_parameter, ..)
exercise
Remember the basic stages of a developing a Visual Basic
application:
We'll set up the controls and write a little bit of code together, but
you'll finish it off yourself.sample program
See how your program should work when you're done by downloading the
sample program to the Desktop and running it a few times:starter project and form files
To save you some time and let us work on the more interesting parts of
this program, we're providing form and project files for you to start
with. Download them into a new folder on your floppy disk:"
Note that almost all of the user interface is already done, with the
exception of one radio (option) button (the one for size grande).
Some of the code has been written, too, including event handlers for
one of the radio buttons and a small subroutine for adding sales tax.
We'll talk more about what you need to add to complete this
program.pricing guidelines
The price of a latte depends on its size (short, tall, or grande) and
number of espresso shots:
Ken Yasuhara <yasuhara@cs.washington.edu>
Last modified: Thu Apr 15 10:13:19 PDT 1999