directing ANTIC how to generate the display. The data processed by this Display List "program" is the screen memory. The output is the graphics display. The kinds of graphics in the output (text vs addressable pixels) is determined by the instructions in the Display List. The display List and the display data are written into RAM by the CPU. ANTIC reads the display List instructions, screen memory, and character set information from RAM using a technique known as direct memory access (DMA). A BASIC or 6502 machine language program's job is to initialize the display—set up the display List instructions, organize screen memory (and character set if applicable), and then direct ANTIC to start the display. After this, ANTIC automatically takes care of generating the screen display. This allows the Atari 8-bit computers to produce complex, mixed-mode displays without direct CPU intervention. Other platforms, even those designed much later, cannot either mix graphics modes in one display, or do so without complex CPU interrupts. ANTIC processes the instructions in the display List, reads the screen memory (and character set data if applicable), translates this information into a real-time stream of graphics data, and sends this data stream to the CTIA/GTIA chip which applies the color to the graphics pixels and outputs the video. Together the two chips provide 6 text and 8 graphics modes (14 total). The more advanced version, GTIA, adds three alternative color interpretations for each ANTIC graphics mode providing a total of 56 (14 times four) graphics modes. However, only the ANTIC graphics modes based on half-color clock pixels are capable of expressing the complete color palette provided by the new color interpretations, and of those modes the ones convenient for use are ANTIC modes 2 (OS Graphics mode 0 text) and ANTIC mode F (OS Graphics mode 8). Thus the reasonable number of unique graphics modes available using the inherent hardware capabilities of ANTIC + CTIA/GTIA is 20–14 ANTIC modes + 3 additional color interpretations each for ANTIC modes 2 and F. Display list instruction overview The Atari display is built as a series of ANTIC instructions each describing a line of text or graphics mode progressively from the top to the bottom of the screen until the desired display area is filled. In effect, the screen is a vertical stack of ANTIC mode instructions. Different modes occupy different numbers of scan lines and use different