1. Introduction

As we all know that the best computers in the world are the C64 and C128. They have their GUI too - the excellent GEOS. GEOS seems very difficult and cryptic for many people, from programmer's point of view. That's not true. The designers of GEOS created a flexible and powerful system, which is easy to use and program.

Coding GEOS in C? That's something new. It is possible now - with Ulrich von Bassewitz's cc65 package and my GEOSLib you are able to create GEOS applications in no time.

GEOSLib supports a subset of the standard cc65 libraries. Whenever possible native Kernal functions are used (e.g. memset is an alias for FillRam), however not all are supported. E.g. string functions like strcmp, strcpy are doubled with native CmpString, CopyString because the latter can handle only 256 byte strings. Keep this in mind when you write your program. If you don't need long strings simply use functions from the Kernal, the resulting code will be smaller.

dio - direct disk access is available, but you might have problems with devices other than 1541, 1571 or 1581. RAM drives emulating these should work.

conio - simple console input-output is available for command line applications. This implementation assumes that one character does fit in 8x8 cell, so output with default BSW font, which is has 9 points, might be a bit messy. There is no color support in GEOS 2.0 so color functions are disabled. Both 40 and 80 column modes are supported and automatically detected.

tgi - TGI driver for GEOS that supports both 40 and 80 column modes but mode can not be changed between tgi_init and tgi_done.

joy - JOY driver for GEOS that supports only joystick, not current pointing device.

It is safe to use these standard includes and their contents: assert.h, conio.h, dio.h, errno.h, em.h, geos.h, joystick.h, modload.h, mouse.h, stdlib.h, string.h, tgi.h, time.h

For time.h functions systime() and clock() note that the resolution is one second.

Functions from the headers above are either standard C library functions or cc65-specific, in either case they are not GEOS specific and so they are not described here.

I am an assembler programmer and GEOSLib was designed in such way that cc65 could emit the best available code (well, the best as for machine :-). Many of the void foo (void) functions are just raw calls to the Kernal (assembled just as jsr _foo), look in gsym.h, where you can find many definitions of standard GEOS locations. Access to these addresses is optimized by cc65 to simple lda and sta. Don't be afraid to use C syntax.

1.1 Requirements

You don't need a C64 or C128 for development. The only hardware requirement is a PC capable of running cc65. You do however need C64 or C128 emulator and GEOS disk images (.d64) to test your programs.

The software needed:

• cc65 Excellent package containing a C crosscompiler, a crossassembler and a linker, you can get it from: http://www.cc65.org/
• VICE This is a portable C64, C128 and few other Commodore computers emulator, you can obtain it from: http://www.viceteam.org/. The VICE package contains the c1541 program that is able to convert/unconvert GEOS files to disk images.
• The Star Commander This tool is only for DOS. You will need it for transferring object files from a PC to a 1541. There's also one important ability of this tool - it automatically un-converts .cvt files into GEOS native format on disk image files. Check out: http://sta.c64.org/sc.html
• cbm4linux A Linux kernel module that allows for communication with a 1541 and other Commodore IEC bus drives. It can be a replacement for Star Commander if you only want to transfer files to a disk and unconvert using GEOS program for this purpose. Check out: http://www.lb.shuttle.de/puffin/cbm4linux

VICE and cc65 are portable - they run on variety of platforms - DOS, Win32 and UNIX. GEOSLib only needs cc65.

Update: starting from v2.5.0 GEOSLib is a part of the cc65 package as its GEOS support library.

1.2 Legal

I want to thank Uz for his cc65 package, Alexander Boyce for his excellent GEOS Programmer's Reference Guide and BSW for GEOS.

GEOSLib is covered by the same license as cc65. You can find the whole text among documentation. I would really appreciate if you would like to send me your comments, suggestions, questions, changes, bug reports etc. I will also appreciate if you will just give me a sign that you are using GEOSLib - not especially something big and important, mail me even if you are just playing with it.

You can send postcards with hellos to:

Maciej Witkowiak, ul. Slowackiego 6/57, 77-400 ZLOTOW

POLAND

e-mail: ytm@elysium.pl