Editing Atari BASIC (section)

===Graphics and sound===
Atari BASIC supports sound, (via the {{mono|SOUND}} statement), graphics ({{mono|GRAPHICS, SETCOLOR, COLOR, PLOT, DRAWTO}}), and controllers ({{mono|STICK, STRIG, PADDLE, PTRIG}}).{{sfn|Manual|1980|p=54}} The {{mono|SOUND}} statement sets one of hardware's 4 square-wave channels with parameters for volume, pitch and distortion.

Advanced capabilities of the hardware such as higher pitch resolution, high-pass filters, digitised sound and waveforms, player/missile graphics ([[sprite (computer graphics)|sprites]]), redefined character sets, scrolling, and custom graphics modes are not supported by BASIC; these will require machine language routines or PEEK/POKE statements. A few of the 16 basic character/graphics modes supported by the hardware cannot be simply accessed from BASIC on the Atari 400/800 as the OS ROMs do not support them. These include some multicolour character modes (ANTIC modes 4 & 5), descender character mode (ANTIC mode 3) and the highest resolution 2 and 4-color modes (ANTIC modes C & E, 160x192 pixels). The only way to access them is via {{mono|PEEK/POKE}} or machine language, setting the ANTIC registers and Display List manually. The OS ROMs on the XL/XE added support for these modes except for ANTIC mode 3, which requires a character set redefined in RAM to operate correctly.<ref>{{cite web|title=ATR: chpt.15: Display Lists|url=http://www.atarimax.com/freenet/freenet_material/12.AtariLibrary/2.MiscellaneousTextFiles/showarticle.php?44}}</ref>

Bitmap modes in BASIC are normally set to have a text window occupying the last four rows at the bottom of the screen so the user may display prompts and enter data in a program. If a 16 is added to the mode number invoked via the GRAPHICS statement, the entire screen will be in bitmap mode (e.g. GRAPHICS 8+16). If bitmap mode in full screen is invoked Atari BASIC will gracefully switch back into text mode when program execution is terminated, avoiding leaving the user with an unresponsive screen that must be escaped by typing a blind command or resetting the computer.

Bitmap coordinates are in the range of 0 to maximum row/column minus one, thus in Mode 6 (160x192), the maximum coordinates for a pixel can be 159 and 191. If Atari BASIC attempts to plot beyond the allowed coordinates for the mode a runtime error occurs.