TweetFollow Us on Twitter

Hello World
Volume Number:2
Issue Number:5
Column Tag:The ABC's of C

Starting with Hello World

By Bob Gordon, Apropos Publications, Minneapolis, MN

Welcome to How to C. This series will explore use of the C language on the Macintosh for those who don't know C and may have fairly limited experience programming the Mac. Put another way, if you often have the feeling that you don't know what's going on, this is a place to get your bearings.

You'll find the following items useful to have around if you want to do more than program vicariously:

• Using the Macintosh Toolbox with C by Takatsuka, Huxham, and Burnard (Sybex, 1986). This will serve as our 'text.' It is currently the best available book on C on the Mac. We will generally follow their order of topics.

• The C Programming Language by Kernighan and Ritchie (Prentice-Hall, 1978). If you are going to use C, you need this book. It is an amazingly clear and concise discussion of the language.

• Inside Macintosh. Mainly because the first book does not cover everything.

• A C development system. A number of compilers are available. We'll focus on Consulair's Mac C because the Using the Macintosh Toolbox book uses it, and because it uses MDS. If you're using a different compiler, don't worry. C is one of the more portable languages (between compilers and machines), and I'll try to point out differences when they appear.

I'll also mention other useful sources of which I am aware. If you have any favorite books or articles, send me a note so we can share the information.

Why Use C / Why Not Use C

C was designed to be suitable for systems programming. As such, it is very flexible and allows programmers to do pretty much as they please. C is often characterized as a 'medium level' language. It offers the control mechanisms and data structures of a higher level language but at the same time allows access to the hardware and the ability to handle data in any way that seems suitable at the time. The compilers typically generate fairly fast, compact code.

This flexibility is not without its costs, however. It is very easy to make a real mess of things (and generate incendiary devices on the Macintosh) by not getting the types of parameters correct. And some C notation can be downright cryptic. It is easy to make C code unreadable.

In spite of the problems, I prefer C to Pascal. I could usually do what I wanted with Pascal (depending on the compiler), but I knew I was cheating. And I could never be sure the technique would work the same way with a different compiler.

Problems Using C on the Macintosh

One problem with C vis-à-vis the Macintosh is that much of the C literature and many of the standard library functions assume you are using Unix or a Unix-like operating system. As you may have noticed, the Macintosh does not. This poses an additional set of problems for learning C on the Mac. The compiler makers follow two approaches. Some ignore Unix; others make the Mac look like it's running Unix.

A second problem is that the Macintosh operating system assumes applications will be written in Pascal. This presents problems in at least two areas: strings and parameter passing.

A C string is an array of bytes with a terminating zero (a byte of all zero bits, a binary zero, the null character, represented in C by \0). A Pascal string, as far as the Macintosh is concerned, is an array of bytes consisting of a leading byte containing the number of bytes in the string followed by the bytes of the string. Obviously sending a C string to a Toolbox function is not going to yield any sort of desired result. The compiler makers have solved this problem in two ways. Some compilers automatically convert the string when its passed; others provide a C function to do the conversion that you call before calling the Toolbox function (and another function to reconvert the string). Check your compiler's documentation to see what it does.

The parameter passing problem involves a number of issues: where parameters are passed (stack or registers), the order in which they are passed, and how complex data types are passed. Most of the time you need not to be concerned with this at all; your compiler will do the necessary translations. In some cases (with some compilers) you must be aware of the difference.

Getting Started

The first program we'll do is the first program in Kernighan and Ritchie. This will force us to figure out how to set up our compiler, and use the editor, compiler, and linker. Now, at this point I should simply recount my experiences in getting "hello, world" to appear on my screen. Unhappily, I only recently received the compiler so I haven't done it yet. I also do not have two Macs so excuse me while I figure this out.

This month I've got Mac C™ from Consulair. It comes with three booklets of documentation, a letter from the author Bill Duvall, and some information sheets. One sheet describes the contents of the four disks. They include a public domain ram disk program written in Mac C called RamStart, so the first thing I did was to set up a ram disk.

Using RamStart is a bit exciting. A help button is available, but if you don't click it fast enough, RamStart goes ahead and makes the ram disk. I don't remember exactly how I found that out: it is, of course, in the instructions, but you can't read the instructions unless you click help. Catch 22. Actually, the program is quite easy to use. Simply put what you want in the ram disk in the same folder with RamStart, and it creates the disk with those files in it. With Mac C, you may not have a ram disk larger than 280 K bytes (on a 512 K machine) or the compiler will run out of room.

The Mac C package includes Edit, the four window mouse-driven program editor. Edit allows transferring directly to the compiler so you can invoke the compiler directly from Edit.

hello, world

Using Edit, I typed in the first program most people learning C try, a program to print "hello, world" on the screen.

#include  "stdio.h"

/* traditional first C program */
main()  
{
  printf("hello, world"); 
}

That's the program. If you have never seen a C program before, there is a lot to examine even in this.

The first line specifies an include file. This is a separate file that you wish to include as part of the compilation. These files typically contain constants, references to external functions, new symbols, and macros, but they can contain any code you wish to include.

Here are some parts of the stdio.h that comes with Mac C:

// stdio.h  

The double slash means comment to the end of the line. This is not standard.

// Copyright 1984 Consulair Corporation.
// All rights reserved

// Aug 30, 1984 2:43 PM: New File
// Standard UNIX IO library defs for MacC

    #define ERROR -1
    #define EOF -1
    #define NULL 0
    #define MAXLINE 255
    #define FILE int

The defines are instructions to the C preprocessor. These supply names to some oft-used values. In a program, you can use the name and the preprocessor will replace it with the value. By the way, standard C practice requires the "#" be in the first column. Mac C allows it anywhere on the line as long at is is preceded only by white space.

// Standard Routines

  extern char putchar();
  extern char fputc();
  extern long putl();
  
  extern int printf(...);

There are references to external functions. External functions are functions defined in another file. For the compiler to work correctly, it needs to know the type of object returned, if any. Here we see that putchar returns a type char, putl returns a long, and printf returns an int. Most C compilers have a separate include file for each chapter in Inside Macintosh to provide the necessary definitions.

To return to our program, the next line is:

/* traditional first C program */

This is a comment. The "/* */" bracket comments.

main()

Every C program must have one and only one main function. It is where execution starts. Function names always have parentheses after them even if they have no parameters.

{
  printf("hello,world");
}

The braces define a block of code that is handled as one line for program control purposes. They are similar to Pascal's begin-end.

The only piece of code that does anything here is printf. It is used to write strings on the screen (the standard output device). It is not actually part of the language but is part of the standard library. The semicolon is a line terminator.

A few comments are in order concerning other compilers. Mac C creates a TTY window for the standard C I/O functions. Other compilers may write directly to the desk top or require that you create a window for them. You will have to check the documentation.

Next month we'll look at some more basic C concepts and start dealing with using C in the Macintosh environment.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Sierra Cache Cleaner 11.0.3 - Clear cach...
Sierra Cache Cleaner is an award-winning general purpose tool for macOS X. SCC makes system maintenance simple with an easy point-and-click interface to many macOS X functions. Novice and expert... Read more
NeoFinder 7.0.1 - Catalog your external...
NeoFinder (formerly CDFinder) rapidly organizes your data, either on external or internal disks, or any other volumes. It catalogs all your data, so you stay in control of your data archive or disk... Read more
Sketch 42 - Design app for UX/UI designe...
Sketch is an innovative and fresh look at vector drawing for the Mac. Its intentionally minimalist design is based upon a drawing space of unlimited size and layers, free of palettes, panels, menus,... Read more
Quicken 4.4.3 - Complete personal financ...
Quicken makes managing your money easier than ever. Whether paying bills, upgrading from Windows, enjoying more reliable downloads, or getting expert product help, Quicken's new and improved features... Read more
Apple Safari 10.0.3 - Apple's Web b...
Note: The direct download link is currently unavailable. It is available in the OS X 10.11.6 release, as well as in the Apple Security Updates. Apple Safari is Apple's web browser that comes with OS... Read more
Apple iTunes 12.5.5 - Play Apple Music a...
Apple iTunes lets you organize and stream Apple Music, download and watch video and listen to Podcasts. It can automatically download new music, app, and book purchases across all your devices and... Read more
Apple macOS Sierra 10.12.3 - The latest...
With Apple macOS Sierra, Siri makes its debut on Mac, with new features designed just for the desktop. Your Mac works with iCloud and your Apple devices in smart new ways, and intelligent... Read more
Lyn 1.8.5 - Lightweight image browser an...
Lyn is a fast, lightweight image browser and viewer designed for photographers, graphic artists, and Web designers. Featuring an extremely versatile and aesthetically pleasing interface, it delivers... Read more
iClock Pro 3.4.7 - Customize your menuba...
iClock Pro is a menu bar replacement clock for Apple's default clock. iClock Pro is an update, total rewrite and improvement to the popular iClock. Have the day, date and time in different fonts and... Read more
Opera 42.0.2393.137 - High-performance W...
Opera is a fast and secure browser trusted by millions of users. With the intuitive interface, Speed Dial and visual bookmarks for organizing favorite sites, news feature with fresh, relevant content... Read more

Clash Royale gets some serious balance u...
| Read more »
Ironhide Game Studio prepares for a busy...
Kingdom Rush breathed fresh life into the tired tower defense genre way back in 2012. The game was a robust challenge that somehow managed to lift you up, rather than leaving you feeling crushed and hopeless. The rich array of unit types and... | Read more »
Collect pets and sling arrows in Arcane...
Mobile gaming is a crowded market, but regular updates are a good way to keep us attention-short players keen. The brand new content in Arcane Online is a prime example. Published by Japanese developer Gala, Arcane Online is a fantasy MMO that... | Read more »
Super Mario Run dashes onto Android in M...
Super Mario Run was one of the biggest mobile launches in 2016 before it was met with a lukewarm response by many. While the game itself plays a treat, it's pretty hard to swallow the steep price for the full game. With that said, Android users... | Read more »
WarFriends Beginner's Guide: How to...
Chillingo's new game, WarFriends, is finally available world wide, and so far it's a refreshing change from common mobile game trends. The game's a mix of tower defense, third person shooter, and collectible card game. There's a lot to unpack here... | Read more »
Super Gridland (Entertainment)
Super Gridland 1.0 Device: iOS Universal Category: Entertainment Price: $1.99, Version: 1.0 (iTunes) Description: Match. Build. Survive. "exquisitely tuned" - Rock Paper Shotgun No in-app purches, and no ads! | Read more »
Red's Kingdom (Games)
Red's Kingdom 1.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0 (iTunes) Description: Mad King Mac has kidnapped your father and stolen your golden nut! Solve puzzles and battle goons as you explore and battle your... | Read more »
Turbo League Guide: How to tame the cont...
| Read more »
Fire Emblem: Heroes coming to Google Pla...
Nintendo gave us our first look at Fire Emblem: Heroes, the upcoming mobile Fire Emblem game the company hinted at last year. Revealed at the Fire Emblem Direct event held today, the game will condense the series' tactical RPG combat into bite-... | Read more »
ReSlice (Music)
ReSlice 1.0 Device: iOS Universal Category: Music Price: $9.99, Version: 1.0 (iTunes) Description: Audio Slice Machine Slice your audio samples with ReSlice and create flexible musical atoms which can be triggered by MIDI notes or... | Read more »

Price Scanner via MacPrices.net

13-inch Touch Bar MacBook Pros in stock for $...
B&H Photo has the new 2016 13″ Touch Bar MacBook Pros in stock today and on sale for up to $150 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 13″ 2.9GHz/512GB Touch Bar... Read more
9-inch 32GB Space Gray iPad Pro on sale for $...
B&H Photo has the 9.7″ 32GB Space Gray Apple iPad Pro on sale for $549 for a limited time. Shipping is free, and B&H charges NY sales tax only. Read more
15-inch 2.2GHz Retina MacBook Pro on sale for...
Amazon has 2015 15″ 2.2GHz Retina MacBook Pros (MJLQ2LL/A) on sale for $1749.99 including free shipping. Apple charges $1999 for this model, so Amazon’s price is represents a $250 savings. Read more
Deal alert! 13-inch 2.0GHz MacBook Pros for $...
B&H Photo has the new 2016 13″ 2.0GHz non-Touch Bar MacBook Pros in stock today and on sale for $225 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 13″ 2.0GHz MacBook Pro... Read more
Free LibreOffice Portable 5.2.4 Complete Offi...
PortableApps.com and The Document Foundation have announce the release of LibreOffice Portable 5.2.4. LibreOffice Portable is an Open Source full-featured office suite — including a word processor,... Read more
Apple Planning Three New Tablets For 2017 – D...
Digitimes’ Rebecca Kuo and Joseph Tsai say that unnamed insider sources report Apple having three new tablets in the pipeline for 2017 release: a 9.7-inch model with a friendly price range, a new mid... Read more
Roundup of 15-inch Touch Bar MacBook Pro sale...
B&H Photo has the new 2016 15″ Apple Touch Bar MacBook Pros in stock today and on sale for up to $150 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 15″ 2.7GHz Touch Bar... Read more
Apple refurbished iPad Pros available for up...
Apple has Certified Refurbished 9″ and 12″ Apple iPad Pros available for up to $160 off the cost of new iPads. An Apple one-year warranty is included with each model, and shipping is free: - 32GB 9″... Read more
16GB iPad Air 2, Apple refurbished, available...
Apple has Certified Refurbished 16GB iPad Air 2s available for $319 including free shipping. A standard Apple one-year is included. Their price is $60 off original MSRP for this model. Read more
Apple iMacs on sale for up to $120 off MSRP
B&H Photo has 21″ and 27″ Apple iMacs on sale for up to $120 off MSRP, each including free shipping plus NY sales tax only: - 27″ 3.3GHz iMac 5K: $2199 $100 off MSRP - 27″ 3.2GHz/1TB Fusion iMac... Read more

Jobs Board

*Apple* & PC Desktop Support Technician...
Apple & PC Desktop Support Technician job in Manhattan, NY Introduction: We have immediate job openings for several Desktop Support Technicians with one of our most Read more
*Apple* & PC Desktop Support Technician...
Apple & PC Desktop Support Technician job in Stamford, CT We have immediate job openings for several Desktop Support Technicians with one of our most well-known Read more
*Apple* Retail - Multiple Positions - Apple,...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
*Apple* Site Security Manager - Apple (Unite...
# Apple Site Security Manager Job Number: 54692472 Culver City, California, United States Posted: Jan. 19, 2017 Weekly Hours: 40.00 **Job Summary** The Apple Read more
*Apple* macOS Systems Integration Administra...
…most exceptional support available in the industry. SCI is seeking an Junior Apple macOS systems integration administrator that will be responsible for providing Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.