The A-code interpretation language was developed by Level 9 around 1979, to create their text based adventure games.
It was very advanced for its time. One of its strong points was the high compression on text. That compression allowed quite big games fit into very limited computers and mainly distributed by cassettes.
The resultant code was common for all platforms, some smaller machines had shorter descriptions though.
- A-code v1: Used for the very first Level 9 games. Spectrum games in this format had black text on a grey background.
- A-code v2: Used for Level 9 games released between 1984 and 1985. It introduced the yellow text on a black background which would later become standard.
- A-code v3: Introduced in 1986, it was the version used for the largest number of games.
- A-code v4: Introduced in 1987, it was used on all new games from then on.