Amiga Screens: A Primer

This explains how Amiga "screens" are literal, independently controlled display areas on classic Amiga hardware (focusing on OCS) that can differ in resolution and colour depth and be opened, positioned and switched or even dragged at will. Colours are indexed from per-screen palettes (12-bit on OCS), and pixels are stored in planar bitplanes: more bitplanes yield more palette indices (up to five bitplanes/32 colours on OCS, or eight/256 on AGA). Low-res on PAL is roughly 320×256 (high-res 640×256), with tricks such as overscan, HAM (Hold-And-Modify) and EHB (Extra Half‑Brite) to expand visible colours. A dedicated co-processor called the copper can change palette and modes per scanline, enabling copper gradients and seamless stacking of different-resolution screens so a system can show many more apparent colours and effects than a single static framebuffer would allow.

Those graphics choices paid off in memory frugality and real multitasking: small, differently configured screens let multiple programs run concurrently without wasting RAM, while the hardware makes scrolling, repositioning and resolution switches instant. The environment supports dual playfields where the top screen’s colour zero becomes transparent, hardware sprites layered between playfields, and rapid screen switching or dragging for quick context changes. Examples include AMOS and Deluxe Paint workflows and a filmed demo on an Amiga 600 that showcases smooth audio/graphics multitasking; compared with modern windowed desktops, the model favors full-screen, tightly integrated graphics tasks even if screen dragging is mainly a nostalgic flourish.