Impulse invariance
Template:Infobox book De Re Atari is a book that was written by Atari employees in 1981 and published by the Atari Program Exchange the year after. It contains detailed descriptions of the advanced features of the Atari 8-bit family of home computers, much of which was not available in other sources.
The book was sold unbound, as a shrink-wrapped set of three-hole punched pages.
Background
An article on Player/Missile Graphics by De Re Atari coauthor Chris Crawford appeared in Compute! in 1981:
Another article by Crawford and Lane Winner appeared in the same month in BYTE:
Early versions of many of De Re AtariTemplate:'s chapters appeared in BYTE in 1981 and 1982 in a series of ten articles:
- Template:Cite news
- Template:Cite news
- Template:Cite news
- Template:Cite news
- Template:Cite news
- Template:Cite news
- Template:Cite news
- Template:Cite news
- Template:Cite news
- Template:Cite news
The series was based on Atari's confidential, 8-bit development documentation written in 1979-1980 for third-party developers under non-disclosure agreements. The articles and De Re Atari were the first public, official publication of Atari 8-bit technical information.
Description
Individual chapters are devoted to making use of the features of the platform, which included ANTIC and the display list, "graphics indirection" in the form of color support in the GTIA and customized character sets, player/missile graphics, using the VBI and display list interrupts (aka HBI/Raster interrupt), smooth scrolling and sound, including a discussion of "volume only sound" which offered higher-resolution volume control for digitized sample playback. Additional chapters covered utilities in the operating system, Atari DOS and Atari BASIC, and design of intuitive human interfaces.
How to make use of these features was often not obvious. For instance, Atari's sprite implementation, player-missile graphics, used a register to indicate the position of sprite on the screen, but required the user to copy the sprite pattern up or down in memory to move it along the axis. Likewise, vertical smooth scrolling was quite simple, but horizontal scrolling required a custom display list that created a "virtual screen" as wide as the scrolling playfield. De Re not only talked about these issues, but provided sample implementations and discussed potential alternate implementations.
Crawford, the lead author of the book, used many of these features in the seminal wargame Eastern Front (1941) released the previous year. Eastern Front made extensive use of smooth scrolling, custom character graphics, and some use of player-missile graphics and basic sound. Another author, Jim Dunion, used custom display lists in the DDT tool (a 6502 debugger) to produce a partitioned, IDE-like display.
The original edition is now out of print but available for viewing on a site maintained by Kevin Savetz, the Atari Archives.