Green Screen
The text-based character interface used to interact with AS400 and IBM i systems. Named for the green monochrome display terminals originally used. A key modernization target.
Green screen refers to the 5250 terminal interface used to operate AS400 and IBM i systems. The name derives from the green phosphor monochrome monitors that were standard with AS400 systems in the 1980s and 1990s. The 5250 interface is a character-based, block-mode display protocol where screens are composed of fixed fields and data is sent to the host only when the user presses a function key. IBM i still uses the 5250 architecture natively, and many IBM i applications present green screen interfaces to users today, often through 5250 emulator software running on Windows PCs. Green screen modernization is a common IBM i initiative where the underlying IBM i application logic is preserved while a web or GUI front-end is built to replace the character interface. Options include screen scraping/web-enabling tools, API-based modernization, and complete application rewrites.