Summary 1

(tutorials — next summary)

This is what we learned in the Squares tutorial.

Objects

All Revolution programs are made from objects.  There are:

• the mainstack, which is the program
• cards, of which we had only one
• buttons, fields etc. which are placed on cards

Objects have properties such as name, location, visibility, opaqueness and others, that may be set by the inspector.  A selected object shows 8 resize handles with which it can be reshaped.

Objects react to messages.

Messages get sent when events happen.

Program Development

There are two modes:

1. Development mode, which is when you write handlers, create and move objects etc.  The select tool is active.
2. Run mode, which is when you let the program do its thing.  The browse tool is active.

Scripts and Handlers

Each object has one script, which is a set of handlers.  A message to which an object must react must have a corresponding handler.  There may also be handlers for other actions invented by us.

Statements

Handlers are made up of program statements.  We saw:

• the assignment statement:  put something into container
• the if-then-else statement
• the exit statement:  it terminates execution of the handler immediately
• the answer statement:  it tells the user something and expects a response

Containers

Containers hold the values we put into them.  We used two types of container:

1. Fields:  they are visible on the screen
2. Variables:  they are inside handlers and exist only during the time the handler runs.

Rules for writing program code

It is always good to be very consistent in how you write your programs.  This helps you to understand your program when you have to read it and it avoids errors.  We saw one rule:

1. Names of objects must always be written between double quotes.

There will be many other rules.  Essentially you make up your own.  I will follow mine in the tutorials.  You are free to adopt them, change them, take inspiration from them or hate them .

(tutorials — next summary)