- Decimal computer
Decimal computers, computers which have a decimal architecture, represent numbers and/or addresses in decimal, and provide instructions to operate on those numbers and/or addresses directly; examples of encoding used are BCD, Excess-3, two-out-of-five code, ASCII, and EBCDIC.
Many early computers, for example the ENIAC, IBM 702, IBM 705, IBM 650, IBM 1401, IBM 1620, IBM NORC, IBM 7070, IBM 7080, Electrodata 200, UNIVAC I, UNIVAC II and UNIVAC III used decimal arithmetic (IBM 1401 addresses were a combination of decimal and binary arithmetic). Some had a variable wordlength, which enabled operations on numbers with a large number of digits.
Later, several microprocessors offered limited decimal support. For example, the 80x86 family of microprocessors provide instructions to convert one-byte BCD numbers (packed and unpacked) to binary format before or after arithmetic operations . These operations were not extended to wider formats and hence are now slower than using 32-bit or wider BCD 'tricks' to compute in BCD (see ).
The 68000 provided instructions for BCD addition and subtractions , these instructions were removed when the Coldfire instruction set was defined, and all IBM mainframes also provide BCD integer arithmetic in hardware.
Decimal arithmetic is now becoming more common; for instance, three decimal floating-point types with two encodings have been added to the new IEEE 754 standard, with 7, 16, and 34-digit decimal significands..
The IBM Power6 processor, the IBM System z9, and the IBM System z10 have implemented these types using the Densely Packed Decimal scheme for encoding the digits of the significand (binary encoding is used for the exponent)., the first and third in hardware and the second in microcode.
- ^ "MASM Programmer's Guide". Microsoft. 1992. http://webster.cs.ucr.edu/Page_TechDocs/MASMDoc/ProgrammersGuide/Chap_06.htm. Retrieved 2007-07-01.
- ^ "Motorola M68000 Family Programmer's Reference Manual". http://www.freescale.com/files/archives/doc/ref_manual/M68000PRM.pdf. Retrieved 2007-07-01.
- ^ "DRAFT Standard for Floating Point Arithmetic P754". 2006-10-04. http://754r.ucbtest.org/drafts/archive/2006-10-04.pdf. Retrieved 2007-07-01.
- ^ [|Cowlishaw, Mike]. "General Decimal Arithmetic". IBM. http://speleotrove.com/decimal/. Retrieved 2008-04-08.
Wikimedia Foundation. 2010.
Look at other dictionaries:
decimal computer — dešimtainis kompiuteris statusas T sritis fizika atitikmenys: angl. decimal computer vok. decimale Rechner, m; Dezimalrechner, m rus. десятичная вычислительная машина, f; десятичный компьютер, m pranc. machine à calculer décimale, f; ordinateur… … Fizikos terminų žodynas
computer science — computer scientist. the science that deals with the theory and methods of processing information in digital computers, the design of computer hardware and software, and the applications of computers. [1970 75] * * * Study of computers, their… … Universalium
Computer music — is a term that was originally used within academia to describe a field of study relating to the applications of computing technology in music composition; particularly that stemming from the Western art music tradition. It includes the theory and … Wikipedia
Computer memory — types Volatile RAM DRAM (e.g., DDR SDRAM) SRAM In development T RAM Z RAM TTRAM Historical Delay line memory Selectron tube Williams tube Non volatile … Wikipedia
Computer: A History of the Information Machine — Author(s) Martin Campbell Kelly and … Wikipedia
Computer senility (Red Dwarf) — Computer senility is a fictional concept developed in the Red Dwarf television series that considers how a sentient computer might develop mental instability if left alone for millions of years. Computer senility would therefore be a product of… … Wikipedia
Decimal Computation — is a textbook by Hermann Schmid. First published in 1974 by John Wiley Sons (ISBN 047176180X) and reprinted in 1983 by Robert E. Krieger Publishing Company (ISBN 0898743184), the book comprises twelve chapters providing detailed description of… … Wikipedia
Computer numbering formats — The term computer numbering formats refers to the schemes implemented in digital computer and calculator hardware and software to represent numbers. A common mistake made by non specialist computer users is a certain misplaced faith in the… … Wikipedia
Computer number format — A computer number format is the internal representation of numeric values in digital computer and calculator hardware and software. Contents 1 Bits, bytes, nibbles, and unsigned integers 1.1 Bits 1.2 … Wikipedia
Decimal — For other uses, see Decimal (disambiguation). This article aims to be an accessible introduction. For the mathematical definition, see Decimal representation. Numeral systems by culture Hindu Arabic numerals Western Arabic (Hindu numerals)… … Wikipedia