The Early Atari Computers

There was a time when the Atari home computers were the only way to get graphics onto a display. In order to make this possible, you had to own at least a black and white TV and hook it up to your computer. Enter the Atari Altirra Emulator!

Once you had the Atari components hooked up, you had the option of saving data to either a cassette or diskette. If you wanted to save data on cassette tapes you needed to own a special type of tape recorder that read data into the computer’s memory and also allowed you to write that out back to the tape.

Then there was the ability to write data faster to a floppy disk. This required the use of a disk drive. The disk drive could hold much more information than on a cassette and the recovery rate was often more successful.

These days, you no longer need to own an Atari home computer, since tools known as “emulators” were created. The most popular emulator for the Atari is called the Atari Altirra emulator. Many of the screenshots you will find on this website are taken from Altirra snapshots.

How to download Altirra. Click on the button below and you will have a fresh copy downloaded to your computer. Then you will need to unzip it and install it on your system. Once you have that up and running, continue back on this article.

Altirra is now Installed

The next thing is learning how to use it. It works very similar to many emulators out there and mirrors concepts of the original Atari computers. In order to access Basic you will need to get access to ROM (binary data) that contain the data as found on the original Atari chips.

Atari DOS 2.5 and above

With the purchase of an original Atari driver, in the early days, users got a free copy of Atari DOS 2.5 or a later version included. With the emulator, you can also locate the ROM for Atari DOS. I have included a screenshot so you can see a directory listing on my computer to see what you need to get the emulator working properly.

Once you finally have it installed it will open up a self start screen. This is identical to holding down the Option key on the original Atari computers, as was a way to test if the computer experienced any problems with the memory, graphics, and sound.
These were also a great way to test the Atari Console keys, such as Select, Start, and Option.
Our next step is to install the file called ATARIBAS.ROM so we can access Atari Basic on the emulator and begin working on creating some cool Atari programs for fun.

Installing the Basic ROM

With Altirra open, click on the File menu and then select Attach Cartridge. One the Windows Explorer window opoens, look for the directory where you installed the ROMs and select it. For example I found the Atari folder and selected ATARIBAS.ROM to load into Altirra.

Then another window appears that says Select Cartridge Mapper. You can click on OK and leave it set to 8K. Finally the Basic Ready screen loads and appears as seen in this screenshot.

This is identical to the original Atari computers that required a BASIC cartridge to load the Basic Programming ROMs into memory, and Assembly language with use of the Atari Assembler Editor cartridge.

Features of the Atair Altirra Emulator

Since Atari Altirra loads in a Windows environment, you can maximize the window or grab the bottom right corner and enlrage it.

Look under the System menu and you will see Warm Reset. If you select this option, Atari Altirra will execute a “warm start”, which is identical to pressing the Reset key on the computer.

Below that you will see an option for Cold Reset. If you have a physical Atari 800/Xl/XE computer, and hold down the Reset key for a few seconds, release it, the Atari computer will go into a “cold start”, which resets everything back to when you first turned on the computer.

There are many other options on the Altirra menus that could be explored, but since we are only focusing on Atari Basic for now, they are not necessary.

Connecting Atari DOS

The same way you would insert an Atari DOS 2.5 floppy disk into a disk drive (such as a 1050), you can “emulate” this in Atari Altirra also. Open up the File menu again and this time select Disk Drives. When the dialog box opens you will see a similar screenshot (as seen here).

Each of the Drives are listed from D1-D8. For this example we will use only D1 (drive 1). to the right look for the three dots and click there. The Windows explorer window will open and you will need to search for the file called DOS25.XFD. This is used to load in the ROMs for Atari 2.5 DOS. Once you are done click on the Open button and then close the Disk drives window by selecting the OK button.

Activating DOS 2.5 Mode

Next in order to activate the Atari in DOS mode, select the System menu again and click on Warm Reset.
When the READY prompt appears again, you can type the command DOS and you will finally see the Atari DOS menu. Now you can also save the programs to file.

Formatting a blank disk

In order to be able to save our programs when using the Atari Altirra emulator, we need a way to format a disk virtually. Open up the File menu and select Disk Drives.

After this click on the area that shows Off and select R/W (rewrite). You can also click on the plus sign to control whether you want a single or double sided diskette format.

On the line for D1, click on the area that is defaulted to Off and select R/W. Then click on the Save button over to the write, name your file, and when you click on Save it will now be contained as an Altirra file with the extension .ATR. Notice that once you are back at the Disk drives window that the area for D1 is now populated with the name you created. Finally click the Ok button to accept these settings.

Format with DOS 2.5

The next step is to format this disk to be used with DOS 2.5. Type the command DOS. When the Atari DOS menu appears, select the option I for FORMAT DISK. You will then see the message WHICH DRIVE TO FORMAT?

Since we already setup the virtual drive for D1, type D1. The emulator will then prompt you with another message that says TYPE “Y” TO FORMAT DISK 1. Once you press the Enter key, the diskette begins formatting when it’s done you will see the message SELECT ITEM or RETURN for MENU. Then press the B key to exit back to Basic. Now we can begin typing in any program and save them normally, which we will explore next.

Writing our Atari Basic Program

When back at the Ready prompt screen, type the command LIST to see the program already contained in memory. We will begin typing in the game program and when we are done we will save it.

Add Your Heading Text Here

Once the program has been completely typed in, it is time to save it with a command. This is the same command used on the original Atari 400/800/XL/XE computers. The Atari Altirra emulator simulates this as seen below. The screenshot also depicts how it will appear on the screen.

Atari Basic Program Output

Finally, we get to see the output of the program we typed in. It’s supposed to be a maze that reveals itself over time. I hope you enjoyed this session as much as I did creating it for you all.
Feel free to leave comments below or questions.

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