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The IBM 709 was an early computer system introduced by IBM in August 1958. It was an improved version of the IBM 704 and the second member of the IBM 700/7000 series of scientific computers. The improvements included overlapped input/output, indirect addressing, and three "convert" instructions which provided support for decimal arithmetic, leading zero suppression, and several other operations. The 709 had 32,768 words of 36-bit memory and could execute 42,000 add or subtract instructions per second. It could multiply two 36-bit integers at a rate of 5000 per second.〔(IBM 709 at Columbia University history page )〕 An optional hardware emulator executed legacy IBM 704 programs on the IBM 709. This was the first commercially available emulator prior to 1960. Registers and most 704 instructions were emulated in 709 hardware. Complex 704 instructions such as floating point trap and input-output routines were emulated in 709 software. The 709 was built using vacuum tubes. IBM introduced a transistorized version of the 709, called the IBM 7090, in November 1959. The FORTRAN Assembly Program was first introduced for the 709. ==Registers== The IBM 709 had a 38 bit accumulator, a 36 bit multiplier quotient register, and three 15 bit index registers whose contents were subtracted from the base address instead of being added to it. All three index registers could participate in an instruction: the 3 bit ''tag'' field in the instruction was a bit map specifying which of the registers would participate in the operation, however if more than one index register was specified, their contents were combined by a logical or operation, not addition.〔IBM 709 Reference Manual, Form A22-6501-0, 1958〕p. 12 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「IBM 709」の詳細全文を読む スポンサード リンク
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