The Atari 400 and 800 came out in 1979. The hardware included the ability to overlay sprites ("players" and the smaller "missiles") over the display. AFAIK, this capability is called "Player/Missile graphics", or PM graphics.

I seem to recall that some games came out exploiting PM, but that the general public didn't know how these effects were done until a magazine article came out to explain them. It could be this article in Compute!, January 1981, which singled out Star Raiders as using PM graphics.

(Questions below edited to fit forum format.)

When and how did the existence and technical details of Player/Missile graphics functionality first become public knowledge?

Is there any indication that Atari initially took action to keep this information secret / undocumented?

  • 2
    Ads would show the great games that professionals created, or the general ease of use of programming for amateurs. No reason, for a general purpose home computer, to show the details of the internals in advertising. Unless you were a game developer, you wouldn't buy an Atari because of these capabilities - you would buy it for general use or to play the games others wrote. Aug 17, 2022 at 17:42
  • 2
    I have the strong sense that I've read somewhere that Atari just didn't offer good documentation on its 8-bit computers for a long period, but cannot currently substantiate that. This 1984 book opens with "Surprise! Atari has a secret feature that sets it apart ... called Player-Missing Graphics" but is aimed at BASIC programmers so feigning surprise may be part of the sales pitch towards those who are just now starting to try to look beyond the limits of BASIC.
    – Tommy
    Aug 17, 2022 at 20:07
  • 9
    Unfortunately, the question closed before I could publish my answer. De Re Atari (1982), serialized in BYTE magazine the previous year, was, to my knowledge, the first time the inner workings of Atari's P/M graphics were publicly described. Prior to that, developers had to sign a nondisclosure agreement with Atari for the information.
    – Jim Nelson
    Aug 17, 2022 at 23:19
  • @JimNelson I've edited the question and asked for it to be reopened.
    – Nimloth
    Aug 18, 2022 at 2:31

2 Answers 2


In the early days of Atari's 8-bit machines, Atari treated their inner workings as trade secrets, in particular their custom graphics and sound chips. Third-party developers could only receive technical documentation on those secrets if they signed a nondisclosure agreement. (Ted Nelson complained bitterly about this situation in his introduction to The Creative Atari.)

Something changed at Atari, though, and the company shifted course. In 1981, several Atari employees began publishing articles in the computing press on the Atari's internals: player-missile graphics, display lists, sound, and more. These articles started in January 1981 (in BYTE and Compute!, which you linked to above) and continued into the next year.

In 1982, this information was collected and published in a single book, De Re Atari, which—for Atari enthusiasts and professionals—quickly developed a reputation as the Bible for the Atari. It was one of biggest sellers for the Atari Program Exchange.

As blogger Atari_Ace points out, it's not that player-missile graphics et al. were unknown by third-party developers before this information was published. No doubt some reverse-engineered the secrets on their own, or had access to the knowledge via those who worked for the right companies. But the revelations of the De Re Atari authors formally introduced the technology to the computing public.

Strangely enough, Atari later became known as one of the more open companies in the emerging microcomputer market. The Atari BASIC Source Book includes the complete source code for Atari's BASIC cartridge as well as a detailed explanation of its workings. Ian Chadwick in his Mapping the Atari thanks the company for its "'open system' policy." Make of that what you will.

  • 1
    Chadwick's "Mapping the Atari" felt like the culmination of the steady flow of technical info that you describe. Strange that it took almost 5 years after the intro of the 400/800 to have such a definitive technical resource for the would-be programmers. Apple and Commodore were way faster in getting technical info into the hands of programmers for their machines. Interestingly, the Amiga RKM references shipped concurrently with Miner's new machine.
    – Brian H
    Aug 18, 2022 at 18:09

In the late 1970s and early 1980s, many popular personal computers were a cross between a video game console and a practical computing device. Manufacturers generally tried to focus their advertising on the latter aspect of their machine. Even though the quality of video games for a console would be a major factor in consumers' product choices, it's important to recognize that to a much greater extent than today, computers were often purchased by parents largely for the use of their children.

If advertisements for computer #1 were to cite its ability to play great video games, but those for computer #2 were to advertise practical computing features, many parents would have insisted on buying computer #2 regardless of the child's preferences. If, however, both computers advertised practical computing features, then parents would be more likely to ask their child which machine to buy. If the games that were available for computer #1 were vastly superior to those for computer #2, the children would likely be aware of this whether or not the computer manufacturer mentioned it in their advertising.

  • True, that's pretty much what happened in my case. I wanted a VIC-20, convinced my parents to buy one. The selling points were price, programmability in BASIC, colour text and graphics on a normal TV screen, and some promise of useful software (recipes and accounting, yeah right). I started programming... but I got the Omega Race cartridge before I even got the cassette deck. It took me a year, maybe, before I found a book that explained enough about the graphics chip to let me understand how Omega Race was done and (once I had enough RAM) do bitmapped graphics of my own.
    – Nimloth
    Aug 19, 2022 at 15:08
  • @Nimloth: The Programmers Reference Manual supplies enough information to describe what one would need to do in order to implement a game like Omega Race, though hosted development tools for the VIC-20 were rather lacking. I think it would have been fairly easy to build an adapter that would allow hooking up a second cassette deck to the user port, and that a VIC-20 with 16K of expansion and two cassette decks would probably be a workable albeit minimalist development platform for developing games of that complexity.
    – supercat
    Aug 19, 2022 at 15:18
  • True, but the Programmer's Reference wasn't available in stores in my area. The book I found at the public library was "Le livre du VIC" from Belgian author Benoît Michel: benoitmichel.be
    – Nimloth
    Aug 19, 2022 at 15:23
  • @Nimloth: Actually, a facility I would think would have been useful for practical software development on something like a VIC-20 would have been a cartridge with 11K of RAM filling out the address space up to 0x4000, EPROM slots for 8Kx8 EPROMs at 0x4000, 0x6000, and 0xA000, along with an EPROM programmer. With suitable tools, one could split the design of something like Omega Race into two separate 8K sections in such a way as to maximize the number of rebuilds that would just require changing one or the other.
    – supercat
    Aug 19, 2022 at 15:26

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .