This is a calculator which uses Reverse Polish Notation, or RPN. A full write-up in Japanese (Google Translate link) carries an impressive level of detail about the project, but in short ...

The Minister of Development explained that several main housing projects have and are being carried out including Phase 2 of the RPN Kampung Lugu and Phase 7 of the RPN Tanah Jambu projects. Yang ...

HP famously built the first portable scientific calculator, the HP-35, although its reverse-Polish notation (RPN) might be a bit of a head-scratcher to those of us who came up in the TI world of ...