If you want to try your hand at writing some 8-Bit code for the Commodore 64 and you have a Mac, I recommend the following setup:
You can download a Mac OS X Binary Distribution of the VICE emulator from the Mac OS X VICE Team's page. I got the Vice Mac OS X 10.5 Cocoa Universal Binary, Version 2.2. Untar it, drag the App to your Application's Folder, and you're good to go:
According to backplane.com, the latest version of DASM should be hosted at Atari2600.org, but that link 404's. If you go to the root of Atari2600.org the homepage talks about some legal dispute between Atari and the owner of Atari2600.org. Likely some kind of copyright/trademark issue. Although the page indicates that those legal issues were resolved and the original site's content will soon be restored -- it has been like that for years. So I just grab the Older, 2.1.6 version of DASM directly from backplane.com.
If you have XCode installed, you should be able to just untar the DASM's source, cd into it, and then "make" -- you'll get a "bin/dasm" executable you can put in your path:
In your DASM folder, create two directories: "code" and "drive". In "code", create a file named "flashy.asm" and enter:
processor 6502 org $c000 start sei lda #
flash sta 789 cli rts flash inc $d020 jmp $ea31
That's the traditional Commodore version of "Hello, World!": the program installs an raster interrupt that flashes the border's color. The program itself isn't that important for now -- you just want to see if your compiler is working. Now, from the DASM directory, you can assemble it into your "drive" directory with:
./bin/dasm code/flashy.asm -o drive/flashy.prg
If all goes well, you'll have a file "drive/flashy.prg" you'll want to load into your Commodore Virtual Machine.
The easiest way to connect your Commodore Virtual Machine to your Mac's File System is to go to the "Settings" Menu of the VICE Emulator and choose "Peripheral Drives" to bring up this dialog:
Make sure "Enable IEC Drive" is checked, and then click the "Mount" Button. Navigate to the "drive" directory you created and click "Open". Now close the dialog and choose the "Settings" Menu and "Save current settings" so you don't need to do that each time you restart the Virtual Machine.
Now, you can access your "drive" directory from within the Commodore 64 Virtual Machine and can edit assembly language programs on your Mac, cross-compile them, and then load and run programs easily from within the Commodore 64 virtual machine:
Isn't that great?