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ELC language reference
Commenting your code
ELC app structure
An empty ELC program
Hello world
Functions
Defining variables
Function parameters
Using variables
Function return values
IF decisions
WHILE loops
FOR loops
Arrays of variables
Library functions
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Defining variables
Variables allow a computer to remember things for you while an app is running. Think of them like this shoe box - a
place you can put something, store it, and get it back later...
We can give each of these variables a name, a bit like writing a label on the front. The label on the shoe box above
shows it is called VarName.
There are two types of variables in ELC: number variables; and word variables. Number variables are used for storing
numbers, which can be either negative or positive. Word variables are used to store anything from one letter up
to sentances as long as you like.
Variable names can be anything you like provided they don't include one of the characters that has another meaning (such
as '+' (add), '-' (subtrcat), '*' (multiply), '/' (divide), '%' (modulus), '(', ')', '{' or '}', '=' (equals),
'>' (greater than), '<' (less than), '>=' (greater than or equals), '<=' (less than or equals), '!=' (not equals), ',' or
space). They also can't be one of the special ELC keywords (GLOBAL, LOCAL, FUNCTION, IF, ELSE, ELSEIF, WHILE, FOR, TO, STEP).
Finally, they can't be the name of a function.
The way we show if a variable is to store numbers or words is whether it has a '$' character on the end. Word variables
have this, number variables do not.
Variables can either be accessed anywhere in an app (global variables), or only in one function (local variables) depending
on how they are set-up (in programming we call this declaring variables). If you like, to get you started, you can
just use global variables but as your programming skill grows you may think "I just need this variable in this function so
I'll declare it as a local variable"). Using local variables prevents your code getting clogged up with lots of global
variables that are only really used in one or two places.
Global variables are declared using the GLOBAL keyword before the START function.
Local variables are declared using the LOCAL keyword inside the function where they are to be used.
Good practice means if you need to use variables often across your code then define them as global variables so you
don't need to keep passing them as parameters. But if you have variables that are only needed within a function then
define them as local variables within that function as this makes your code easier to understand.
Here's an example of some global variables and some local variables. The code doesn't actually use them - we'll come
onto that later in the tutorial...
// ===================================================
// This ELC app defines some global variables and has
// some functions that define some local variables.
// They are not actually used in this example, that
// will come in the next section
GLOBAL GlobalNum1,GlobalNum2
GLOBAL GlobalWords1$,GlobalWords2$
FUNCTION START()
{
LOCAL LocalNum
LOCAL LocalWords$
GFX.WRITELINE("Hello world")
}
// ===================================================
// Simple empty function
FUNCTION DoSomeMaths(Num)
{
LOCAL TempNum
}
// ===================================================
// Another simple empty function
FUNCTION MixSomeWords(Words$)
{
LOCAL TempWords$
}
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Next, function parameters...
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