Fundamentals of BASIC

Variables

Naming

The following list shows some variable names that are allowed by AppStudio:

text
LLAMAS
Jupiter
W1Spec
SouthPark

And some that are not allowed:

1table          'starts with a number 
X&Ycords        'uses special character & 
first counter   'has a space 
%correct        'does not start with a letter
print           'Keyword

Variables

• All variables are of type Variant.
• No explicit types
• Variable get their types from the value that is assigned.

Numeric

• Floating point: 5e-324 (negative) to 1.7976931348623157e+308 (positive)
• Integers: reliable to 15 digits.
• Hex: 0x500 = 1280
• Octal: O500 = 320

Booleans

• True or False.

Colors

• From “#000000” to “#FFFFFF” (black to white)
• color = (red*65536) + (green * 256) + blue

Strings

• Maximum length depends on memory, up to 2 billion characters

Arrays

• Dim A(9) declares an array with 10 elements
• Dim B(8,8) creates a two dimensional array
• Elements can be referred to as A(3), B(2,3), etc.
• Dim statement has to be in each Code Module
• The following notation is also OK: a[3], B[2][3}
• Array elements do not exist until they are assigned.

Collections

• Like an Array, but uses string values to index

Dim item1, myCollection(10)
item1="Knuth"

'Create our collection
myCollection[item1] = "firstKey"
Print myCollection[item1]  'displays "firstkey"

Objects

• An object is a collection of named values, called properties

Customer={Name: Lovelace, Age: 195, kids:{Byron: 1, Annabella: 2, Ralph: 3}}
Print Customer.name  'displays "LoveLace"

Classes

'Define a class like this
Function Person(name, gender)
   'Add object properties like this
   this.name = name
   this.gender = gender
End Function

'Add methods like this.  All Person objects will be able to invoke this
Function speakName()
  Print "Howdy, my name is " & this.name
End Function

Person.prototype.speak = Eval("speakName")

'Instantiate new objects with 'new'
bob = new Person("Bob", "M")

'Invoke methods like this
bob.speak() 'Prints "Howdy, my name is Bob"