TweetFollow Us on Twitter

Think C Tutor
Volume Number:5
Issue Number:10
Column Tag:MacOOPs!

A First Look At THINK C 4.0

By Alastair Dallas, Glendale, CA

Note: Source code files accompanying article are located on MacTech CD-ROM or source code disks.

Think C 4.0 First Look

[Alastair Dallas is the president of Software Magic, a developer of (as yet unreleased) Macintosh software. He moonlights as a Sr. Software Designer for the IBM PC side of Ashton-Tate, publisher of FullWrite Professional, Full Impact and dBASE Mac, none of which Mr. Dallas had anything to do with.]

If you are like me, you were surprised by Symantec’s announcement at the end of July that a brand new, object-oriented version of their popular C compiler would be available soon. Rumors that principal author Michael Kahl was working on object-oriented extensions to his LightspeedC package predate the June, 1988 release of version 3.0. When Apple warned us this spring that “you’d better learn object-oriented programming” if you want to program your Mac in the future, perhaps you, like me, were hoping for an object-oriented programming system (oops) that was as accessible as THINK’s LightspeedC to learn with.

THINK C (they dropped the name Lightspeed with this release) is nearly the C version of MacApp we’ve been waiting for. The new version supports Object Pascal-style extensions and a generic application which you can customize. And it’s available now. Symantec must have waited until THINK C 4.0 was ready to ship before announcing it, because my upgrade order was filled in less than a week-much faster than the upgrade to 3.0. The upgrade price is $69 to registered owners, and the retail price of 4.0 is said to be over 50% higher than 3.0.

What do you get for your money? A lot. In addition to the popular integrated compiler, linker, editor, source-level debugger and make facility, this release includes version 1.0 of the THINK Class Library (TCL) which encapsulates most of the standard Macintosh user interface. The C compiler includes improvements making it 95% conformant with the draft ANSI C standard as well as object-oriented extensions which make the THINK Class Library possible.

THINK C 4.0 arrives on four disks, including full source code to a 100% ANSI-conformant library, Macintosh ROM Toolbox “glue” libraries, several example programs (non-oops examples from 3.0 and Art Class, a fairly full-featured MacPaint-type application written using TCL), and template projects (Starter and Pedestal) which you can use to build your own applications.

Two soft-cover books describe the product. The 512-page User’s manual is essentially the 3.0 user’s manual with 250 pages of object-oriented material added as section four. The 37 Core Classes of the TCL are described here, one to a chapter. While the size of the other book, the Standard Libraries Reference, is about the same as it was in 3.0, the content has changed profoundly because the functions and header files are now organized according to the ANSI standard.

If you are familiar with version 3.0, you’ll want to hear exactly what’s new about 4.0:

• Object extensions to C (described below)

• THINK Class Library (almost MacApp for C)

• ANSI C compatibility

• Prototypes for function definitions

• # (stringize) and ## (concatenate) preprocessor operators

• long double type, long double literals

• ANSI standard library w/ glass tty example

• Inline assembler extensions for 68020 and 68881 instructions

• “Once-only” headers

• Multi-segment code resources

• Better cdev (control panel device) support

• Inline assembler functions (makes glue functions more efficient)

Introduction to Object-Oriented Programming

The lecturer at a recent seminar explained that if he wanted to sell his cat just now (to a bunch of programmers), he would advertise it as an object-oriented cat. Object-oriented, the buzzword, has been around since the late 1970s, when BYTE magazine broke the story about Smalltalk (which, legend has it, got Steve Jobs interested in Xerox PARC in the first place).

The term object-oriented may be used to describe almost anything, including a cat, but it almost always promises reusable code. THINK C (TC) is no exception; the system makes it easy to take a generic piece of code and customize it by overriding one or more of its functions. Once you customize the generic window code so that sizing the window maintains its aspect ratio (width / height), you then have a new type of generic window object that you can specialize in other ways for your next project.

Objects are a way of grouping data together with the functions which manipulate that data. All the books tell you that objects mimic the real world, but I think a better example is that objects mimic Macintosh user interface elements. Take windows, for example. A window object has data (the WindowRecord, which includes a grafPort, and perhaps some other variables) and it has certain operations it knows about. These operations are called methods in the literature, but they’re implemented as functions in THINK C. For example, a window can change size, move (drag), hide, show and so on. An application might have several windows, each capable of the same operations, but each window would have a different WindowRecord.

In THINK C, you essentially address the WindowRecord (actually the Window object) and say “hide yourself.” THINK C knows how to find the functions which all Window objects have in common. If you want to customize the Window object as I described above, for example, you create a new object type (called a class) that is derived from the Window class with, in this case, a special “change size” function. If you tell your special Window to do something ordinary like hide itself, THINK C will use the same function that any Window would use for that command-your special Window object only provides the code that makes it different from a normal Window.

For more reading about object-oriented concepts as they apply to the Macintosh, I recommend “Object-Oriented Programming for the Macintosh” by Kurt Schmucker (Hasbrouck Heights, NJ:Hayden, 1986, ISBN 0-8104-6565-5). This book emphasizes MacApp, but describes the Macintosh user interface in object-oriented terms and provides an overview of several oops languages as well, such as Lisa Clascal, Smalltalk and Objective-C.

The most famous object-oriented C is described in “The C++ Programming Language” by Bjarne Stroustrup (Reading, MA:Addison-Wesley, 1986, ISBN 0-201-12078-X). The THINK C manual (p. 9) claims that THINK’s syntax resembles C++ and states that “The extensions are upward-compatible with C++ (i.e., C++ compilers can compile THINK C programs, but THINK C cannot compile all C++ programs).” Because C++ is a superset of the C language, this statement is strictly true, but it is misleading to consider THINK C an implementation of C++. C++ v1.0 implemented several concepts which THINK C left out, and C++ v2.0 has just been released with even more features. The following C++ features are not implemented in THINK C:

• Operator overloading (the ability to define operators like ‘+’ in the context of a particular object)

• Special automatic constructor and destructor methods (all calls are explicit in TC)

• Public vs. private class variables and methods (all are public in TC)

• Friend functions for access to private variables

• Virtual functions

• Inline code expansion (functions defined within class definitions)

• The // characters start a comment that extends to end of the line

• Multiple inheritance (C++ v2.0)

THINK C reserves no new keywords. Instead, identifiers indirect, direct, this and inherited are “interpreted specially in context.” In contrast, C++ programs use the following reserved words:

class

delete

friend

inline

new

operator

overload

public

this

virtual

Like C++, THINK C uses structures for class definitions; methods use the ‘::’ scope resolution operator, as in “myClass::myMethod”; and objects can reference themselves using “this.”

Although on the surface THINK C could be called “C++ Lite,” the two languages are more alike than, say, C and Smalltalk. And the implementation of THINK C is “close to the machine,” in that it was designed specifically to make programming a Macintosh efficient, rather than to satisfy purist notions of language design.

Object Extensions to THINK C

In conventional C, a data structure may be defined without creating a variable or reserving storage space; multiple variable declarations can then reference this structure definition. The structure is an abstract definition and the variables are concrete instances. In THINK C, objects are much the same.

An abstract description of an object is called a class. A class is a structure definition containing variables and functions, as in:

/* 1 */

struct classname : superclass
 
 /* instance variables */
 int myVar; /* for example */
 char myStr[255];
 Rect bounds;

 /* by convention, methods follow instance variables */
 void Init(void);
 void Destroy(void);
 Boolean Hit(Point where);

Superclass is the class from which this class is derived, such as CObject using TCL (root classes have superclass direct or indirect, described in more detail in the manual). The classname can be used without the keyword struct, because THINK C thoughtfully assumes that you want:

typedef struct classname classname

Objects are specific instances of a class. Objects are usually implemented as handles (direct root objects and their descendants are pointers), but THINK C adds an automatic level of indirection for you, so that you declare objects as pointers, and reference their members with the ‘->’ operator:

classname *object;

object->method(myPt);

The file <oops.h> declares functions which act on objects in general: new() creates a new instance of an object class; delete() disposes of an instance; member() tests whether a particular object is a member of a specified class; and bless() assigns an object (loaded externally from a resource, for example) to a particular class.

Any methods (functions) declared for a class must be defined using syntax like:

Boolean classname::Hit (Point where)
 
 return (PtInRect(where, &bounds));

Note that in this example, bounds is an instance variable of this object-THINK C provides an implicit declaration. The variable this is implicitly declared, as well, to allow an object’s methods to refer to themselves. Minimizing global variables is an important part of making code reusable, and objects encourage this practice.

The THINK Class Library

THINK C 4.0 includes a set of predefined classes which implement the standard Macintosh user interface. The 37 Core Classes are described in the User’s Manual. A few highlights (class names begin with ‘C’ by convention):

CApplication - top of the chain of command, supervises documents

CDocument - “the essence of a Macintosh application,” manages a file and a window

CSwitchboard - routes events to all objects

CBartender - handles menu choices (and menuKeys)

CBureaucrat - implements a “chain of command” starting with the current gopher (usually a part of a window). Each link in the chain, like all good bureaucrats, passes anything it doesn’t understand up the chain to its supervisor.

CWindow - handles a window, consisting of one or more panes

CPane - part of a window, e.g., content, scroll bar, grow box, etc.

CPanorama - a scrollable pane (it’s actually a little more complicated-more object classes are involved)

CChore - background or urgent tasks

TCL goes considerably beyond menus, windows and documents. The library (actually a template application) supports printing, file I/O, show/hide clipboard, pictures and editable text. It even makes Undo fairly easy to implement, because each command is an integer and the chain of command is unambiguous.

TCL was apparently entirely written by Gregory H. Dow, who also wrote the Art Class example program. To implement some of the trickier features of Art Class, he extended the Core Classes of TCL and Symantec provides source code to these extensions (More Classes), as well. Although they didn’t make it into the user’s manual, More Classes include:

CTearOffMenu - how much would you pay to avoid figuring these out? But wait, before you answer-you also get...

CSelectorMDEF - supports custom tool and pattern menus

CPictFile - reads, writes MacDraw™ (PICT) files

CPNTGFile - reads, writes MacPaint™ files

CBitMap - displays bitmaps (CBitMapPane makes them scrollable)

CColorWindow - color windows

The beauty of the TCL (and MacApp) is that your application is reduced to the elements which make it distinct from a standard application. It’s no longer necessary to ferret out the specifics by wading through pages of event loop and DoContentClick() code. The main() function of any program using TCL looks something like:

/* 2 */

#include <CApplication.h>

extern CApplication *gApplication;

void main()
 
 gApplication = new(CYourApp);
 ((CYourApp *) gApplication)->IYourApp();

 gApplication->Run();
 gApplication->Exit();

 /* main */

A Simple Example

The manual recommends that your classes (you must override certain classes, such as CApplication) be defined in a “.h” file and implemented in a “.c” file each with the name of the class. That is, a typical project might include:

app.c
CmyApp.c, CmyApp.h
CmyDoc.c, CmyDoc.h

This convention makes a lot of sense and encourages reuse of common classes in multiple projects. However, it means looking at a lot of files in the beginning when you’re trying to figure out how it all works.

On the theory that more than one sort of example helps the learning process-you have to see anything from more than one side to understand it-I’ve written a really simple program using TCL which does far less than the templates provided with THINK C. I’ve grouped the code into one module, too, so that you can see the extent of it.

This example leans on TCL to provide a standard Macintosh application which puts up a window (not a document). TCL implements desk accessories, dragging and sizing the window, MultiFinder support and one command: Quit.

It was necessary to define three new classes: CTutorApp, CTutorDir and CTutorWindow. The standard TCL classes CApplication and CDirector are called abstract classes because they are not pre-implemented and must be overridden (in C++ terms, they are virtual), so we implement our own initialization methods for them.

CTutorApp::ITutorApp calls the standard CApplication::IApplication() function with some boilerplate memory constraints and creates and initializes an instance of CTutorDir, which will control our window.

CTutorDir::ITutorDir calls the standard CDirector::IDirector() function and passes the address of our application object (gApplication) as supervisor. Then it creates and initializes an instance of CTutorWindow.

The only method we override in the standard CWindow class is Close(). We do this so that clicking in the close box of the window will have the effect of Quitting the application. Our CTutorWindow::Close() function performs the window close task by calling inherited::Close() first, and then sends the message Quit() to our application, which performs several shutdown tasks and ends up returning from the Run() function. Our main() then calls gApplication->Exit() to tell our application that we’re really leaving now and finally exits to shell by falling off the end of main().

To compile this application, I “borrowed” a copy of the Pedestal project resource file. Using ResEdit, I changed the MENU resource for the File menu so that only the Quit item remained, and I set the title of the WIND 2000 resource to “Mac Tutor Class Act.” Using a copy of the Pedestal project folder, I included most of the THINK Class Library as separate files, and THINK C did the rest.

Conclusion

If you want to write programs for the Macintosh, you will have to become familiar with object-oriented programming techniques. It makes sense for a lot of reasons, not the least of which is that Apple is warning developers that oops is a prerequisite to many of the things they’re working on. The Macintosh interface is just too complicated to let reinventing the wheel get in the way of writing insanely great applications.

Until now, the only mainstream way to get the benefits of oops was to buy the Macintosh Programmer’s Workshop, buy MacApp and learn to program in Object Pascal. Apple will eventually offer MPW C++ and they plan to offer MacApp for C++ as well. Standards, especially those promulgated by Apple, are a very good thing. But LightspeedC became a de facto standard by being “firstest with the mostest,” and the same could happen with the THINK Class Library. Meanwhile, everything is converging, anyway-MacApp is being ported to C, THINK Pascal will support MacApp eventually, and so on.

The point is, there is no reason to wait for object-oriented programming to come to you. The time is now to dive in and get used to the new programming paradigm. I have seen the future, and it’s object-oriented.

/* MacTutor.c */
#include <CApplication.h>
#include <CDesktop.h>
#include <CDirector.h>
#include <commands.h>

struct CTutorApp : CApplication
 {
 /* no instance variables */
 /* instance methods */
 void ITutorApp(void);
 void DoCommand(long theCommand);
 };
 
struct CTutorDir : CDirector
 {
 /* CDirector is an abstract class, so we must override it */
 void ITutorDir(void);
 };

struct CTutorWindow : CWindow
 {
 /* want to override close for our own nefarious purposes */
 void Close();
 };

extern CApplication *gApplication;
extern CDesktop *gDesktop;

void main(void)
{
 gApplication = new(CTutorApp);
 ((CTutorApp*)gApplication)->ITutorApp();

 gApplication->Run();
 
 gApplication->Exit();  
}/* main */

void CTutorApp::DoCommand(long theCommand)
{
 /* not strictly necessary-here in case we ever want to handle a command 
*/
 switch (theCommand)
 {
 
 default:
 inherited::DoCommand(theCommand);
 break;
 
 } /* switch */
 
 return;
}/* CTutorApp::DoCommand */

void CTutorApp::ITutorApp()
{
 CTutorDir *ourDirector;

 CApplication::IApplication(4, 20000L, 2000L);
 
 ourDirector = new(CTutorDir);
 ourDirector->ITutorDir();
 
 return;
}/* CTutorApp::ITutorApp */

void CTutorDir::ITutorDir()
{
 CDirector::IDirector(gApplication);
 
 itsWindow = (CWindow *) new(CTutorWindow);
 itsWindow->IWindow(2000, FALSE, gDesktop, this);
 
 return;
}/* CTutorDir::ITutorDir */

void CTutorWindow::Close(void)
{
 inherited::Close();
 gApplication->Quit();
 
 return;
}/* CTutorWindow::Close */

/* EOF: MacTutor.c */

 
AAPL
$111.78
Apple Inc.
-0.87
MSFT
$47.66
Microsoft Corpora
+0.14
GOOG
$516.35
Google Inc.
+5.25

MacTech Search:
Community Search:

Software Updates via MacUpdate

LibreOffice 4.3.5.2 - Free Open Source o...
LibreOffice is an office suite (word processor, spreadsheet, presentations, drawing tool) compatible with other major office suites. The Document Foundation is coordinating development and... Read more
CleanApp 5.0.0 Beta 5 - Application dein...
CleanApp is an application deinstaller and archiver.... Your hard drive gets fuller day by day, but do you know why? CleanApp 5 provides you with insights how to reclaim disk space. There are... Read more
Monolingual 1.6.2 - Remove unwanted OS X...
Monolingual is a program for removing unnecesary language resources from OS X, in order to reclaim several hundred megabytes of disk space. It requires a 64-bit capable Intel-based Mac and at least... Read more
NetShade 6.1 - Browse privately using an...
NetShade is an Internet security tool that conceals your IP address on the web. NetShade routes your Web connection through either a public anonymous proxy server, or one of NetShade's own dedicated... Read more
calibre 2.13 - Complete e-library manage...
Calibre is a complete e-book library manager. Organize your collection, convert your books to multiple formats, and sync with all of your devices. Let Calibre be your multi-tasking digital librarian... Read more
Mellel 3.3.7 - Powerful word processor w...
Mellel is the leading word processor for OS X and has been widely considered the industry standard since its inception. Mellel focuses on writers and scholars for technical writing and multilingual... Read more
ScreenFlow 5.0.1 - Create screen recordi...
Save 10% with the exclusive MacUpdate coupon code: AFMacUpdate10 Buy now! ScreenFlow is powerful, easy-to-use screencasting software for the Mac. With ScreenFlow you can record the contents of your... Read more
Simon 4.0 - Monitor changes and crashes...
Simon monitors websites and alerts you of crashes and changes. Select pages to monitor, choose your alert options, and customize your settings. Simon does the rest. Keep a watchful eye on your... Read more
BBEdit 11.0.2 - Powerful text and HTML e...
BBEdit is the leading professional HTML and text editor for the Mac. Specifically crafted in response to the needs of Web authors and software developers, this award-winning product provides a... Read more
ExpanDrive 4.2.1 - Access cloud storage...
ExpanDrive builds cloud storage in every application, acts just like a USB drive plugged into your Mac. With ExpanDrive, you can securely access any remote file server directly from the Finder or... Read more

Latest Forum Discussions

See All

Make your own Tribez Figures (and More)...
Make your own Tribez Figures (and More) with Toyze Posted by Jessica Fisher on December 19th, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
So Many Holiday iOS Sales Oh My Goodness...
The holiday season is in full-swing, which means a whole lot of iOS apps and games are going on sale. A bunch already have, in fact. Naturally this means we’re putting together a hand-picked list of the best discounts and sales we can find in order... | Read more »
It’s Bird vs. Bird in the New PvP Mode f...
It’s Bird vs. Bird in the New PvP Mode for Angry Birds Epic Posted by Jessica Fisher on December 19th, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Telltale Games and Mojang Announce Minec...
Telltale Games and Mojang Announce Minecraft: Story Mode – A Telltale Games Series Posted by Jessica Fisher on December 19th, 2014 [ permalink ] | Read more »
WarChest and Splash Damage Annouce Their...
WarChest and Splash Damage Annouce Their New Game: Tempo Posted by Jessica Fisher on December 19th, 2014 [ permalink ] WarChest Ltd and Splash Damage Ltd are teaming up again to work | Read more »
BulkyPix Celebrates its 6th Anniversary...
BulkyPix Celebrates its 6th Anniversary with a Bunch of Free Games Posted by Jessica Fisher on December 19th, 2014 [ permalink ] BulkyPix has | Read more »
Indulge in Japanese cuisine in Cooking F...
Indulge in Japanese cuisine in Cooking Fever’s new sushi-themed update Posted by Simon Reed on December 19th, 2014 [ permalink ] Lithuanian developer Nordcurrent has yet again updated its restaurant simulat | Read more »
Badland Daydream Level Pack Arrives to C...
Badland Daydream Level Pack Arrives to Celebrate 20 Million Downloads Posted by Ellis Spice on December 19th, 2014 [ permalink ] | Read more »
Far Cry 4, Assassin’s Creed Unity, Desti...
Far Cry 4, Assassin’s Creed Unity, Destiny, and Beyond – AppSpy Takes a Look at AAA Companion Apps Posted by Rob Rich on December 19th, 2014 [ permalink ] These day | Read more »
A Bunch of Halfbrick Games Are Going Fre...
A Bunch of Halfbrick Games Are Going Free for the Holidays Posted by Ellis Spice on December 19th, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »

Price Scanner via MacPrices.net

Invaluable Launches New Eponymously -Named A...
Invaluable, the world’s largest online live auction marketplace, hhas announced the official launch of the Invaluable app for iPad, now available for download in the iTunes App Store. Invaluable... Read more
IDC Reveals Worldwide Mobile Enterprise Appli...
International Data Corporation (IDC) last week hosted the IDC FutureScape: Worldwide Mobile Enterprise Applications and Solutions 2015 Predictions Web conference. The session provided organizations... Read more
The Apple Store offering free next-day shippi...
The Apple Store is now offering free next-day shipping on all in stock items if ordered before 12/23/14 at 10:00am PT. Local store pickup is also available within an hour of ordering for any in stock... Read more
It’s 1992 Again At Sony Pictures, Except For...
Techcrunch’s John Biggs interviewed a Sony Pictures Entertainment (SPE) employee, who quite understandably wished to remain anonymous, regarding post-hack conditions in SPE’s L.A office, explaining “... Read more
Holiday sales this weekend: MacBook Pros for...
 B&H Photo has new MacBook Pros on sale for up to $300 off MSRP as part of their Holiday pricing. Shipping is free, and B&H charges NY sales tax only: - 15″ 2.2GHz Retina MacBook Pro: $1699... Read more
Holiday sales this weekend: MacBook Airs for...
B&H Photo has 2014 MacBook Airs on sale for up to $120 off MSRP, for a limited time, for the Thanksgiving/Christmas Holiday shopping season. Shipping is free, and B&H charges NY sales tax... Read more
Holiday sales this weekend: iMacs for up to $...
B&H Photo has 21″ and 27″ iMacs on sale for up to $200 off MSRP including free shipping plus NY sales tax only. B&H will also include a free copy of Parallels Desktop software: - 21″ 1.4GHz... Read more
Holiday sales this weekend: Mac minis availab...
B&H Photo has new 2014 Mac minis on sale for up to $80 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 1.4GHz Mac mini: $459 $40 off MSRP - 2.6GHz Mac mini: $629 $70 off MSRP... Read more
Holiday sales this weekend: Mac Pros for up t...
B&H Photo has Mac Pros on sale for up to $500 off MSRP. Shipping is free, and B&H charges sales tax in NY only: - 3.7GHz 4-core Mac Pro: $2599, $400 off MSRP - 3.5GHz 6-core Mac Pro: $3499, $... Read more
Save up to $400 on MacBooks with Apple Certif...
The Apple Store has Apple Certified Refurbished 2014 MacBook Pros and MacBook Airs available for up to $400 off the cost of new models. An Apple one-year warranty is included with each model, and... Read more

Jobs Board

*Apple* Store Leader Program (US) - Apple, I...
…Summary Learn and grow as you explore the art of leadership at the Apple Store. You'll master our retail business inside and out through training, hands-on experience, Read more
Project Manager, *Apple* Financial Services...
**Job Summary** Apple Financial Services (AFS) offers consumers, businesses and educational institutions ways to finance Apple purchases. We work with national and Read more
*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
*Apple* Retail - Multiple Positions (US) - A...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.