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This article describes software driven graphics modes for the Atari 8-bit computers. That is, graphics displays reliant on CPU intervention and additional software that enhance the inherent capabilities of the Atari 8-bit computers' ANTIC and CTIA/GTIA graphics chips. These modes use combinations of mixed display lists, scrolling, page flipping, and display list interrupts to achieve displays with alternate resolution and increased color that are not possible using the hardware alone. ==Any Point, Any Color== The ''APAC System'', or ''Any Point, Any Color'' was a software-driven display mode capable of displaying an image using all 256 of the Atari's possible colors. By taking 80×192 mode lines that displayed 16 hues, and those that displayed 16 shades, and either interlacing rows of them, quickly alternating between rows of them, or both, a screen displaying 80×96 or 80×192 pixels in 256 colors could be perceived. APAC was created in early 1987 and later introduced in the magazine A.N.A.L.O.G. Computing, Issue #60, May 1988 in an article by Tom Tanida. The source code was written in 6502 assembly language. APAC used a Display List Interrupt, or DLI, after each line of the screen was drawn to alternate between GTIA Graphics Mode 11 (15 hues) and 9 (15 shades of grey) of the GTIA chip. The hues and luminances would blend together on the screen (usually a television) to create the effect of a palette of 256 visible colors, with the artifact of a thinner, horizontal blank line in between each visible line. APAC used a very basic API consisting of four functions: * Init, used to place the computer into the APAC mode * Exit, used to exit the APAC mode * Plot, used to place a point of a specified color on the screen * Draw, used to draw a line between the last plotted point to the given point A second article for an "APAC-II" mode was hinted at in the original article. This mode would have alternated the GTIA 9 and 11 modes during a vertical blank interrupt, or VBI. The article was neither completed nor published.〔(AtariWiki V3: APAC Graphics mode )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Software-driven graphics modes for the Atari 8-bit computers」の詳細全文を読む スポンサード リンク
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