![]() ![]() ![]() ![]() These formats are still supported in the current design, where they are now called the " hexadecimal floating-point" (HFP) formats. The 360/85 and follow-on System/370 add support for a 128-bit "extended" format. The IBM System/360 supports a 32-bit "short" floating-point format and a 64-bit "long" floating-point format. The extended format occupies three 16-bit words, with the extra space simply ignored. Floating-point arithmetic operations are performed by software, and double precision is not supported at all. The characteristic in both formats is an 8-bit field containing the power of two biased by 128. The latter format makes full use of the CPU's 32-bit integer operations. Standard precision format contains a 24-bit two's complement significand while extended precision utilizes a 32-bit two's complement significand. The IBM 1130, sold in 1965, offered two floating-point formats: A 32-bit "standard precision" format and a 40-bit "extended precision" format. ![]() In a few cases the implementation was merely a software-based change in the floating-point data format, but in most cases extended precision was implemented in hardware, either built into the central processor itself, or more often, built into the hardware of an optional, attached processor called a " floating-point unit" (FPU) or "floating-point processor" ( FPP), accessible to the CPU as a fast input / output device. In many cases the format of the extended precision is not quite the same as a scale-up of the ordinary single- and double-precision formats it is meant to extend. Various manufacturers have used different formats for extended precision for different machines. There is a long history of extended floating-point formats reaching back nearly to the middle of the last century. 1.3 IEEE 754 extended precision formatsĮxtended precision implementations.1.2 Microsoft MBF extended precision format. ![]()
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