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NAR 2 (Serbian Nastavni Računar 2, en. ''Educational Computer'' 2) was a theoretical model of a 32-bit word computer created by Faculty of Mathematics of University of Belgrade professor Nedeljko Parezanović as an enhancement to its predecessor, NAR 1. It was used for Assembly language and Computer architecture courses. The word "nar" means Pomegranate in Serbian. Many NAR 2 simulators have been created — for instance, one was named "Šljiva" (en. ''plum'') as that fruit grows in Serbia, while "nar" does not. ==Instruction structure== NAR 2 processor Machine instructions was made of a single 32-bit machine word and contained: * opcode in 8 most significant bits (bits 24 to 31) * 4 bits (20 to 23) specifying the Index register to use with indexed addressing modes * 4 bits (16 to 19) containing address mode flags: * * bit 19: P (sr. Posredno, en. ''mediated'') - indexed * * bit 18: R (sr. Relativno) - relative to program counter * * bit 17: I (sr. Indirektno) - multi-level memory indirect (note: the address is loaded from specified location and, should it also specify "I" flag the indirect address calculation continues) * * bit 16: N (sr. Neposredno) - immediate * 16 bit ''signed'' parameter value 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「NAR 2」の詳細全文を読む スポンサード リンク
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