378:) was restricted to privileged code, preventing some types of program error. Codewords referenced vectors of data items, sequences of instructions or other codewords . Storage was accessed by reference to a codeword and this was resolved to a conventional address or program counter giving direct access to store when necessary. The system provided functions to create, manage and update codewords, for example changing them to reflect storage management decisions. It also supported an algebraic programming language (called Genie) which was implemented using object-oriented design concepts in 1961. The Genie compiler and associated assembler were unusual in enabling the entire system to be treated as an object-management discipline. Genie was also amongst the first languages to include intrinsic operations on real and complex vectors and matrices.
132:
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340:, R1 (1958–61) and the ICL Basic Language Machine (1963–68). A key feature in the architectures of both machines was control by the hardware of the formation and use of memory references so that the memory could be seen as a collection of data objects of defined sizes whose integrity is protected from the consequences of errors in address calculation, such as overrunning memory pointers (whether by accident or malicious intent).
36:
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439:. The internal representation of codewords was opaque to user programs but specific machine instructions were provided to manipulate them in ways that maintained the data structure. That represented a substantial refinement of the Rice R1 architecture, providing for the efficient management of multiple processes, each having a separate tree-structured data and instruction store.
405:. Both of these require a computer architecture in which the operating system could guarantee the separation, security and integrity of several concurrently-running programs. It seemed clear that the simplified model of architecture derived from the Princeton IAS and followed by all the “von Neumann” models would run into severe difficulties in satisfying that requirement.
464:
In parallel with construction of the BLM a separate evaluation team assessed it in terms of (1) program efficiency (2) operating characteristics (3) coding and debugging costs and (4) system overheads. For meaningful comparison, legacy high-level languages (Cobol, Fortran, file management) were
468:
Levy discusses the wider impact of descriptor-based computer architectures with reference to both the
Burroughs B5000 and the BLM (p. 38) "... whether or not they were long-lived, these machines demonstrated the feasibility of using descriptors and segmentation to greatly increase programming
482:
Changes in semiconductor technology in the 30 years following the development of the BLM led to refinements of the architecture. In the absence of research funding they were evaluated mainly by simulation using low-cost microprocessors and Iliffe's
336:(18 September 1931 – 16 February 2020) was a British computer designer who worked on the design and evaluation of computers that supported fine-grained memory protection and object management. He implemented, evaluated and refined such designs in the
348:
Iliffe attended the EDSAC programming course in
Cambridge in 1952. He eventually learned about computing by running the IBM (UK) service bureau in London. In 1958 he was invited to join the team building the R1 computer at
453:
series of computers developed and marketed by the
Burroughs Corporation. All these descriptor-based computers included hardware mechanisms designed to support the reliable addressing of data segments. They are closely related to
353:, Houston, in which he took responsibility for operating system and language design and implementation. In the next 30 years he put into operation four computers demonstrating and evaluating new concepts in design.
416:. Instead of basing the architecture on a single linear address space, the BLM offered segmented memory addressing, enabling automatic storage management and access within precise security boundaries.
371:. His design included an early instance of dynamic memory allocation and management, enabling programs to acquire storage on demand and automatically recover it when it was no longer accessible.
469:
flexibility for the user, the compilers, and the operating system". Levy also notes that "an excellent discussion of the BLM within the context of modern capability systems appears in Iliffe's
393:
In the early 1960s there was a strong requirement for general-purpose computers to provide for the concurrent execution of multiple user programs, both in the form of
385:
storage structure for multi-dimensional and irregular arrays emerged from the R1 work. It exploits a similar addressing structure but without system enforcement.
479:
In the year 2000 Iliffe received the IEEE Harry H. Goode
Memorial Award "For lifetime achievement in the practice of computer system design and evaluation."
1033:(Reference manual for the Genie language, with information about runtime environment and related utility programs. Attributed by Iliffe to Jane G. Jodeit).
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The BLM design was rejected by ICL management in an internal review of options to select a new architecture for ICL's mainframe products in
December 1969.
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used. It was shown that despite the precision of the addressing mechanism there was no noticeable loss of efficiency or additional system overhead.
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vectors seen in most other systems. He developed a design based on the use of codewords to represent all memory references. A codeword included a
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Iliffe took the engineering view that it should be possible to offer a way, based on the memory management techniques already demonstrated in the
973:
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In the R1 Iliffe and his colleagues introduced a protection scheme for all data objects. The manipulation of references to memory (termed
423:
to ensure the integrity of concurrent programs without resorting to relatively expensive mechanisms involving the frequent swapping of
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Describes the architectural principles, storage organisation and the programming functions of the experimental Basic
Language Machine.
547:
Education: Carpenter
Scholarship to City of London School (1945–1948). Mathematical Tripos at St John's College, Cambridge 1949–1952.
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aimed both at the efficient protection of concurrently-executing programs and the reliable implementation of high-level languages
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Describes the codeword-based system of program and data representation used on the Rice
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The Rice R1 and the BLM were examples of descriptor-based computer architectures that emerged in the 1960s
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Design of computer systems with secure object management and fine-grained program protection; the
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The Basic
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Chapter 2 Early Descriptor Architectures, Chapter 3 Early Capability Architectures
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Notes on the Genie compiler for the Rice University Computer
575:"Harry H. Goode Memorial Award | IEEE Computer Society"
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IEEE Computer Society Harry H. Goode Memorial Award, 2000
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City of London School: John Kenneth Iliffe, Class of 1948
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A Study of Cache Memories for a Parallel/Planar Machine.
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Rice University presents “The Completed Computer,” 1961
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The Use of The Genie System in Numerical Calculations
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Service: Royal Navy 1953–1956. Instructor Lieutenant.
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Sports: President of Otter Swimming Club 1990–1996.
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may be too technical for most readers to understand
798:Iliffe, J. K.; Jodeit, Jane G. (1 November 1962).
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723:"A Brief History of the Rice Computer 1959-1971"
435:specifying the length of a data object and some
739:(mostly written in 1994, and archived by the
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1039:"Storage organization in programming systems"
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589:"John Iliffe | IEEE Computer Society"
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194:Learn how and when to remove this message
176:Learn how and when to remove this message
114:Learn how and when to remove this message
98:, without removing the technical details.
875:"From Torsional Mode Delay Lines to DAP"
139:This article includes a list of general
1104:Ph.D. Thesis, University of London 1989
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313:International Computers Limited
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1037:Jodeit, Jane (November 1968).
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632:10.1093/comjnl/12.3.251
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363:Rice Institute Computer
344:Technical contributions
338:Rice Institute Computer
321:Imperial College London
271:University of Cambridge
160:more precise citations.
939:Buckle, J. K. (1978).
817:10.1093/comjnl/5.3.200
18:Basic Language Machine
1138:IEEE award recipients
1056:10.1145/364139.364152
914:Iliffe, J.K. (1982).
879:Computer Resurrection
661:. London: MacDonald.
657:Iliffe, J.K. (1968).
403:interactive computing
1079:The Computer Journal
839:J.K. Iliffe (1961).
804:The Computer Journal
619:The Computer Journal
357:The Rice R1 Computer
269:St. John's College,
942:The ICL 2900 series
729:on 24 February 2008
334:John Kenneth Iliffe
212:John Kenneth Iliffe
525:, if appropriate.
1075:"Elements of BLM"
918:. Prentice Hall.
852:978-1-4832-2282-0
615:"Elements of BLM"
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298:Scientific career
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