Christopher Strachey

2.1. Birth and Family Background

Christopher Strachey was born on November 16, 1916, in Hampstead, England, to Oliver Strachey and Rachel (Ray) Costelloe. His father, Oliver, was a civil servant in the Foreign Office and the son of Richard Strachey, who was involved in colonial administration in India. Richard's grandfather, Sir Henry Strachey, 1st Baronet, held the title of Baronet. Christopher's elder sister was the writer Barbara Strachey. In 1919, the family relocated to 51 Gordon Square. The Strachey family was closely associated with the renowned Bloomsbury Group, an influential assembly of English writers, intellectuals, philosophers, and artists that included figures such as Virginia Woolf, John Maynard Keynes, and Christopher's uncle, Lytton Strachey. The Strachey family as a whole was prominent, having produced notable individuals in various fields including government, arts, administration, and academia.

2.2. Schooling and University

At the age of 13, Strachey enrolled at Gresham's School in Holt, Norfolk. While he exhibited clear signs of intellectual brilliance, his academic performance there was generally poor. In 1935, he was admitted to King's College, Cambridge, the same college attended by the famous mathematician and computer scientist Alan Turing. Despite the prestige of his university, Strachey continued to show little enthusiasm for his studies. He initially majored in mathematics before transferring to physics. Towards the end of his third year at Cambridge, Strachey suffered a nervous breakdown, an event possibly linked to his personal struggle with coming to terms with his homosexuality. Although he returned to Cambridge, he only managed to achieve a "lower second" in his Natural Sciences Tripos.

3.1. Early Career and Teaching

Due to his academic challenges, Strachey was unable to continue his formal education. He subsequently joined Standard Telephones and Cables (STC) as a research physicist. His initial assignment involved providing mathematical analysis for the design of electron tubes, which were critical components in early radar systems. The complex nature of these calculations necessitated the use of a differential analyser, an early form of mechanical computing machine. This foundational experience with computing machinery ignited Strachey's deep interest in the field, prompting him to begin his own research into computing. An application for a research degree at the University of Cambridge was unsuccessful, and Strachey remained at STC throughout World War II. Following the war, he realized a long-held ambition by becoming a schoolmaster. He took a position at St Edmund's School, Canterbury, where he taught both mathematics and physics. Three years later, in 1949, he transitioned to the more prestigious Harrow School, where he continued teaching for another three years.

3.2. Work at National Physical Laboratory (NPL)

In January 1951, a friend introduced Strachey to Mike Woodger of the National Physical Laboratory (NPL). At that time, NPL had successfully constructed the Pilot ACE, a scaled-down version of Alan Turing's pioneering Automatic Computing Engine (ACE) concept from 1945. In his spare time, Strachey dedicated himself to developing an early version of a program for the game of draughts (known as "checkers" in American English). He completed this program in May 1951. This program is widely considered to be one of the earliest, if not the first, video games ever created. The draughts program was so extensive that it completely exhausted the entire memory capacity of the Pilot ACE. When it was first run at NPL on July 30, 1951, the program initially failed due to programming errors.

Upon learning about the Manchester Mark 1 computer, which boasted a significantly larger memory capacity, Strachey contacted his former university peer, Alan Turing, to obtain the machine's manual. By around October 1951, Strachey successfully transcribed his draughts program into the specific operation codes of the Manchester Mark 1. By the summer of 1952, the program had been refined to the point where it could "play a complete game of Draughts at a reasonable speed." Although Strachey did not formally name this game, Noah Wardrip-Fruin later referred to it as "M. U. C. Draughts."

3.3. Early Computer Music and Creative Software

Strachey was a pioneer in the realm of computer-generated music, creating the first computer music program in England in 1951. He produced the earliest known recording of music played by a computer: a rendition of the British National Anthem, "God Save the King", performed on the University of Manchester's Ferranti Mark 1 computer. Later that same year, a BBC outside broadcasting unit recorded short extracts of three pieces on the Ferranti Mark 1: "God Save the King", "Baa, Baa, Black Sheep", and "In the Mood". In 2016, researchers at the University of Canterbury in Christchurch, New Zealand, successfully restored the original acetate master disc of these recordings.

In the summer of 1952, Strachey further demonstrated the creative potential of computing by programming a love letter generator for the Ferranti Mark 1. This program is recognized as the first example of computer-generated literature, showcasing an early fusion of technology and creative writing. In May 1952, Strachey delivered a two-part talk titled "the study of control in animals and machines" (a discussion on cybernetics) for the BBC Home Service's Science Survey program, further highlighting his broad interests and insights into the intersection of technology and natural systems.

3.4. National Research Development Corporation (NRDC) and Consultancy

From 1952 to 1959, Christopher Strachey was employed by the National Research Development Corporation (NRDC). During his involvement with the St. Lawrence Seaway project, he had the opportunity to visit several prominent computer centers across the United States. During these visits, he meticulously cataloged their respective instruction sets, gaining valuable insights into diverse computing architectures. Subsequently, he contributed to programming both the Elliott 401 computer and the Ferranti Pegasus computer. Alongside Donald B. Gillies, Strachey filed three patents related to computing design, including an innovative design for base registers aimed at program relocation, a technique vital for efficient memory management. He also briefly collaborated with Roger Penrose on the analysis of vibration in aircraft, showcasing his versatility across different scientific applications of computing.

In 1959, Strachey transitioned from his role at NRDC to become an independent computer consultant. In this capacity, he entered into contracts with various organizations, including NRDC, EMI, and Ferranti, working on a diverse array of projects. His consultancy work encompassed critical areas such as the logical design of computers, the development of autocode systems, and, later, the design of high-level programming languages. For a specific contract to develop the autocode for the Ferranti Orion computer, Strachey notably hired Peter Landin, who served as his sole assistant throughout Strachey's period as a consultant.

3.5. University Appointments

Christopher Strachey developed the groundbreaking concept of time-sharing in 1959, submitting a patent application for it in February of that year. He presented his influential paper, "Time Sharing in Large Fast Computers," at the inaugural UNESCO Information Processing Conference held in Paris. During this conference, he shared his visionary concept with J. C. R. Licklider, who would later play a crucial role in the development of the ARPANET. In 1963, the MIT Computation Center formally credited Strachey's paper as "the first paper on time-shared computers," acknowledging its foundational importance to the field. This pioneering work laid the groundwork for modern interactive computing, allowing multiple users to share a single mainframe computer simultaneously.

In 1962, while continuing his consultancy work, Strachey accepted an academic position at the University of Cambridge. His academic career advanced significantly in 1965 when he moved to the University of Oxford. There, he became the first director of the newly established Programming Research Group. Later, he was appointed as Oxford University's first professor of computer science and became a fellow of Wolfson College, Oxford. During his tenure at Oxford, he engaged in a significant collaboration with Dana Scott, a partnership that would lead to revolutionary contributions in programming language theory. In recognition of his pioneering work, Strachey was elected as a distinguished fellow of the British Computer Society in 1971. In 1973, Strachey, alongside Robert Milne, began work on an essay submitted for the Adams Prize competition, which they later expanded into a book. Strachey's voice and presence can also be observed in the recorded Lighthill debate on AI, a notable discussion on the future of artificial intelligence.

4.1. Programming Language Design and Theory

Strachey was a key developer of the Combined Programming Language (CPL), an influential early programming language. His highly impactful set of lecture notes, titled Fundamental Concepts in Programming Languages, formalized the crucial distinction between L-values and R-values, concepts that are fundamental to how variables and memory are handled in many programming languages, famously seen in the C programming language. Strachey is also credited with coining the term currying in the context of programming language semantics, referring to the technique of transforming a function that takes multiple arguments into a sequence of functions, each taking a single argument. While he popularized the term, the underlying mathematical concept existed prior to his work.

4.2. Time-Sharing Systems

One of Strachey's most significant innovations was his conceptualization and ardent promotion of time-sharing systems, which he first proposed in 1959. His seminal paper, "Time Sharing in Large Fast Computers," presented at the inaugural UNESCO Information Processing Conference in Paris, is recognized as the first academic paper to articulate the concept of time-shared computers. This groundbreaking idea revolutionized how computers were utilized, allowing multiple users to interact with a single powerful machine concurrently. By enabling interactive and seemingly simultaneous access, time-sharing drastically improved the efficiency of computing resources and democratized access to powerful machines, laying essential groundwork for modern multi-user operating systems and interactive computing environments.

4.3. Denotational Semantics

Strachey's collaboration with Dana Scott was foundational to the development of denotational semantics. This theoretical framework provided a rigorous mathematical basis for describing the meaning and behavior of programming languages. Prior to this, the semantics of programming languages were often described informally or operationally, making formal reasoning about programs difficult. Denotational semantics allowed for the precise specification of what a program does, independent of any particular machine or implementation. This work was a monumental step in the formal analysis of programming languages, enabling deeper theoretical understanding and facilitating the design of more robust and predictable languages.

4.4. Macro Processors

Strachey was responsible for the design and implementation of the General Purpose Macrogenerator (GPM). GPM was an early and highly influential macro expansion language, designed to allow programmers to define simple text substitutions or more complex code transformations. Its design principles profoundly influenced subsequent macro processing systems. Notably, the widely used m4 macro language, often employed in software configuration and generation, derives much of its conceptual foundation from Strachey's GPM. This pioneering work showcased Strachey's talent as a programmer, with the Japanese source noting that he managed to implement GPM using only 250 machine code instructions, demonstrating remarkable efficiency.

4.5. Early Computer Games

Strachey holds a significant place in the history of video games through his development of a draughts (checkers) program in May 1951 for the Pilot ACE computer. This program is widely regarded as one of the earliest computer games ever created. Despite initial programming errors during its first run on July 30, 1951, Strachey's persistence led him to adapt the program for the Manchester Mark 1, a machine with greater memory capacity. By the summer of 1952, his program could play a complete game of draughts at a reasonable speed, marking a critical milestone in the development of interactive computer entertainment. The game, later named "M. U. C. Draughts" by Noah Wardrip-Fruin, showcased the potential of computers beyond pure calculation, venturing into the realm of recreational and interactive applications.

4.6. Key Computer Science Terminology

Beyond his direct technical inventions, Christopher Strachey made a lasting impact on computer science through his contributions to its fundamental vocabulary. He is credited with defining and popularizing several key terms that are now ubiquitous in the field. Among these are "polymorphism" and "referential transparency." Polymorphism refers to the ability of programming constructs (like functions or objects) to take on different forms or types, allowing for more flexible and reusable code. Referential transparency describes a property of expressions that can be replaced with their corresponding values without changing the program's behavior, a concept central to functional programming and program optimization. These terms remain essential for clear communication and understanding within the computer science community.

6.1. Academic Legacy

The profound and lasting impact of Christopher Strachey's work on academic computer science is formally acknowledged by the Department of Computer Science at the University of Oxford, which established the Christopher Strachey Professorship of Computing in his honor. This distinguished professorship has been held by several eminent figures in the field, including:

These appointments underscore Strachey's enduring influence on theoretical computer science and programming language research, affirming his role as a foundational figure whose vision continues to inspire successive generations of scholars.

6.2. Commemorative Events and Archives

To celebrate the centenary of Christopher Strachey's birth, a special event titled Strachey 100 was held in November 2016 at Oxford University. This commemorative gathering honored his life and research, bringing together academics and enthusiasts. A significant part of the event included a viewing at the Weston Library in Oxford, showcasing items from the Christopher Strachey archive, which is a part of the extensive collection held within the Bodleian Library. These events and the careful preservation of his personal papers and correspondence ensure that his intellectual legacy remains accessible for future generations of researchers and historians, facilitating ongoing study of his pivotal role in computing history.

6.3. Overall Impact and Evaluation

Christopher Strachey's innovative spirit and remarkable foresight profoundly shaped the early development of computer science. His pioneering work in time-sharing systems not only optimized resource utilization but also fundamentally changed the interaction between users and computers, making computing more accessible and interactive for a broader audience. Through his contributions to programming language design, especially with CPL, and his formalization of concepts like L-values and R-values, he provided essential theoretical underpinnings that influenced subsequent language development. His collaboration on denotational semantics offered a rigorous mathematical framework for understanding program behavior, elevating programming language theory to a new level of precision. Furthermore, his early forays into computer music and computer-generated literature, alongside the creation of one of the first video games, demonstrated a visionary understanding of computing's potential beyond mere calculation, extending into creative and recreational domains. Strachey's legacy is that of a trailblazer whose conceptual and practical innovations laid much of the groundwork for the interactive, multi-user, and diverse computing landscape we experience today.