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Legacy systems
Glossary: legacy systems
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The terms that come up once a system has run for twenty years: the AS/400 under its three names, DB/400, the green screen, and the file formats underneath. Below is what each term means and why it matters, assuming no prior knowledge.
The IBM platform
- AS/400, iSeries, IBM i
- Three names for the same system. IBM launched the AS/400 in 1988, renamed the line iSeries around 2000 and later System i; since 2008 the operating system has been called IBM i.
- DB/400
- The database built into the system, today DB2 for i. An ordinary relational database: with the right driver a reporting tool reads from it directly.
- 5250 terminal
- The green screen. Originally a physical device, now almost always an emulator on a PC. The screen layout lives inside the programs themselves.
- RPG
- The language most AS/400 applications are written in. We do not develop in it; our role is on the outside: managing, unlocking, connecting and migrating.
Legacy file formats
- Clipper
- A development environment from the DOS era, with its own index and memo files (.ntx, .dbt) around dBase tables.
- Paradox
- A database format with separate table, index and memo files. A damaged index can often be rebuilt as long as the table itself is readable.
- BDE (Borland Database Engine)
- The database layer under older Delphi applications. Long unmaintained; we prefer to read such tables directly.
- Code page
- The character set an old file was stored in, usually a DOS variant. Without conversion, accents and punctuation become unreadable.
Come across a term that is not here? Send it over. The name of a file format is often enough to judge whether the data can still be read.
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