Tagged architecture

In computer science , a tagged architecture [1] [2] [3] is a particular type of computer architecture where each word of memory is made of a tagged union , being divided into a number of bits of data, and a tag section that describes the type of the data: how it is to be interpreted, and, if it is a reference, the type of the object that it points to.

Two notable series of American tagged architectures were the Lisp machines , which had tagged support at the hardware and opcode level, and the Burroughs wide systems , which had a data-driven tagged and descriptor-based architecture. Another “exemplary” instance was the architecture of the Rice Computer . [4] Both the Burroughs and Lisp machine were examples of high-level language computer architectures , where the tagging was used to support a high-level hardware level.

In addition to this, the original The Xerox Smalltalk implementation used the least-significant bit of Each 16-bit word as a tag bit: If It Was clear Then The hardware Would accept it as an aligned memory address while If It Was Set It was Treated as a (shifted) 15-bit integer. Current Intel documentation mentions that the lower bits of a memory address may be similarly used by some interpreter-based systems.

In the Soviet Union, the Elbrus series of supercomputers pioneered the use of architectures in 1973.


  1. Jump up^ Memory Management Glossary: ​​Tagged architecture
  2. Jump up^ Feustel, Edward A. (July 1973). “On the Advantages of Tagged Architecture” (PDF) . IEEE Transactions on Computers : 644-656. Archived from the original on January 21, 2013 . Retrieved January 21, 2013 .
  3. Jump up^ Feustel, Edward A. (1972). “The Rice Research Computer – A tagged architecture” (PDF) . Proceedings of the 1972 Spring Joint Computer Conference . American Federation of Information Processing Societies (AFIPS). pp. 369-377. Archived from the original on July 27, 2014 . Retrieved July 27, 2014 .
  4. Jump up^ Thornton, Adam. “A Brief History of the Rice Computer 1959-1971” . Archived from the original on February 24, 2008 . Retrieved January 31, 2013 . (mostly written in [or before] 1994, and archived by theWayback Machineon a date indicated [by “20080224”] in the URL)

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