Apple IIgs Programming (K Fest)

An Introduction to
Apple IIgs Programming
in a High Level
Language
by
Mike Stephens

First Presented at
Mt Keira Fest 2009

Topics To Cover
 What programming languages are available?
 An overview of Complete Pascal
 A quick introduction to Pascal
 Your very first program!
 Introducing the Toolbox
 Using the Toolbox

What programming languages are
available?

BASIC Programming
 Applesoft BASIC with Toolbox extensions
(Interpreted)
 TML BASIC
 Micol Advanced BASIC
 GSoft BASIC (Interpreted)

ORCA Languages
 ORCA/Integer BASIC
 ORCA/Pascal
 ORCA/C
 ORCA/Modula-2

Complete Pascal
My recommendation for anyone wanting to get
started with high level language programming on
the Apple IIgs is….

You guessed it!

Complete Pascal.

An overview of Complete Pascal

Complete Pascal
Positives:
 Is freely available

 Is a compiled language

 Has full access to the Apple IIgs Toolbox

 Has an uncomplicated and easy to learn
development environment
 Has some nice extensions to Pascal

Complete Pascal

Negatives:
 Has some bugs in the GUI resource editor

 Produces larger & less efficient compiled code
(as compared to ORCA/Pascal)
 Can not link to assembly code (however, inline
assembly code is possible)
 No debugger

A quick introduction to Pascal

Pascal Overview (continued)
 In Complete Pascal, comments start with
a (* and end with a *) OR comments may start
with a { and end with a } .
 Examples of comments:
 (* this is a comment *)
 { so is this! }

Pascal Overview
The basic structure of a Pascal program is:
PROGRAM ProgramName (FileList);

CONST
(* Constant declarations *)

TYPE
(* Type declarations *)

VAR
(* Variable declarations *)

(* Subprogram definitions *)

BEGIN
(* Executable statements *)
END.

 Rules for identifiers:
 Must begin with a letter from the English alphabet.
 Can be followed by alphanumeric characters (alphabetic
characters and numerals) and possibly the underscore (_).
 May not contain certain special characters, many of which
have special meanings in Pascal.
~ ! @ # $ % ^ & * ( ) + ` - = { } [ ] :
" ; ' < > ? , . / |
 May be any of the reserved words (see the TML Pascal II
manual for details).

 Pascal is not case sensitive!
 MyProgram, MYPROGRAM,
and mYpRoGrAm are all equivalent.
 For readability purposes, it is a good idea to use
meaningful capitalization.
 An identifier can be any length so long as it can
fit on one line, however, in Complete Pascal
only the first 255 characters are significant.

Pascal Array Types
 An array type defines a structure that has a set
number of components, and all of the
components are of the same type.
 Array types in Pascal take the form:
ARRAY[ <INDEX TYPE> ] OF <COMPONENT TYPE>

 For example, an array of 100 real numbers:
array[1..100] of real

Pascal Record Types
 A record type consists of a specified collection
of components called fields, each one capable of
being a different type. Each field of a record
type must specify its type, and the name of its
identifier. For example:
record
year: integer;
month: 1..12;
day: 1..31;
end

Complete Pascal Strings
 A string type is a succession of characters having a dynamic
length attribute and a constant dimension attribute of 1 to 255.
 The current value of the length attribute for a string type is
returned by the standard function length.
 A null string is a string type value that has a dynamic length of
zero.
 For example:
var
myString : string;
myLength : Integer;

myString := ‘Hello Mt Keira Fest!’;
myLength := Length(myString); { myLength equals 20 }

Pascal Assignment
 Once you have declared a variable, you can store
values in it. This is called assignment.
 To assign a value to a variable, follow this
syntax:
variable_name := expression;

 For example:
myFloat := 10.559;

Pascal Relational Operators
 The operand types and the corresponding results for
Relational operations are shown in the following table:

Operator Meaning
< Less than
> Greater than
= Equal to
<= Less than or equal to
>= Greater than or equal to
<> Not equal to

Complete Pascal Control Statements
 The GOTO statement will pass control to another part
of the program located in the same block.
 The CYCLE statement forces a repetition statement to
immediately execute the next iteration of a loop.
 The LEAVE statement forces the immediate exit from
a repetition statement loop.
 The HALT statement will stop the execution of the
program immediately.

Pascal Procedures
 A procedure declaration associates an identifier with a block of
statements.
 A procedure is called by using the procedure identifier and the
current parameters required by it.
 An example of a procedure declaration:
procedure Num2String (N: integer; var S: string);
var V: integer;
begin
V := Abs(N);
S:='';
repeat
S:= concat(Chr(V mod 10 + ord('0')),S);
V:= V div 10;
until V = 0;
if V<0 then S := Concat(('-',S);
end;

Pascal Functions
 A function declaration associates an identifier with a block of statements, able
to be called in order to calculate and return a value of the specified type.
 An example of a function declaration:

function Num2String(N: integer;) : string;
var V: integer;
S: string;
begin
V := Abs(N):
S := '';
repeat
S := concat(Chr(V mod 10 + ord('0')),S);
V := V div 10;
until V = 0;
if V<0 then S := concat('-',S);
Num2String := S;
end;

Pascal Units
 Complete Pascal supports the use of Units,
which are stand alone modules (or libraries)
which may define any number of procedures
and functions.
 Units are compiled separately.
 Units are made accessible to a main program or
to other Units via the USES clause.

Hello Mt Keira Fest!
 Open Complete Pascal and select FileNew
from the menu.
 In the Create File box, type HelloKFest.p and
click New.
 You will then be presented with a new window
in which to type your first Complete Pascal
program.

Hello Mt Keira Fest! (continued)
 Type in the following:
Program HelloKFest;

begin
writeln(‘Hello (Mt) K(eira)Fest!!’);
readln;
end.

Compile Your Code
 You can check the syntax of your code without
compiling it by clicking CompileCheck Syntax,
however, most times you will probably just want
to compile to disk by clicking CompileTo Disk.
 If everything went smoothly, you should have
just created your first Complete Pascal textbook
application!

Running Your Program
 You can execute your program by:
 Exiting Complete Pascal and running your program
from the Finder; or
 From within Complete Pascal click GSOSTransfer
and select your HELLOKFEST application and
click Transfer.

The Apple IIgs Toolbox
 The Apple IIgs Toolbox is comprised of a number of
specialised tool sets.
 Each tool set is made up of a number of routines that
you can use from within your own programs.
 The Toolbox routines are designed to hide the
complexity of dealing with the IIgs hardware.
 To become really familiar with the Apple IIgs Toolbox,
you need to have the 3 Toolbox reference manuals +
the GS/OS manual.

What Do the Toolsets Provide?
 Quickdraw II - Graphics routines
 Memory Manager – allocating/deallocating
memory
 Sound Toolset – load and play digitized sounds
 SANE – floating point routines
 Window Manager – create & handle windows
 Event Manager – handle system events
 Plus more!

Complete Pascal & the Toolbox
 Complete Pascal comes complete with interface
files necessary to hook directly into the Toolbox
routines
 As a rule of thumb, each tool set is defined as a
Unit, which you can use from your
programs/units by adding the appropriate tool
set interface file to the USES clause.

Apple IIgs Programming (K Fest)

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