Important People in Computing and Programming

Why it matters: The rule gcd(a, b) = gcd(b, a mod b), ending when b = 0, is the course's model example of both a loop-based and a recursive method.

Euclid's original version used repeated subtraction; the remainder form is the modern equivalent. Each step makes the numbers smaller, which is the standard argument that the algorithm always stops.

Why it matters: His name stands behind the central idea of the course: a finite, precise sequence of steps that solves a problem.

The word "algebra" comes from al-jabr in the title of his book on equations (c. 820). Latin translations of his arithmetic spread decimal place-value notation in medieval Europe.

Why it matters: F(n) = F(n−1) + F(n−2) is the classic exercise for loops and for showing why naive recursion repeats work.

The sequence was known earlier in Indian mathematics; the name "Fibonacci sequence" was popularised in the 19th century by Édouard Lucas. Its terms grow so fast that even a Java long overflows after about 92 terms.

Why it matters: Every number, character and instruction in a computer is stored in the binary system that Leibniz described.

His "Explication de l'arithmétique binaire" appeared in the memoirs of the Paris Academy of Sciences. He also dreamed of a formal language in which reasoning could be carried out by calculation.

Why it matters: Changing the cards changed the pattern without changing the machine, an early form of a program kept separate from the hardware.

Babbage planned to feed the Analytical Engine with Jacquard-style cards, and punched cards later carried data and programs well into the 1970s.

Why it matters: The course compares a summing loop (n additions) with Gauss's formula (one multiplication and one division) to show that algorithms differ in cost.

Gauss became one of the most important mathematicians in history, working in number theory, astronomy, geodesy and magnetism. Gaussian elimination and the Gaussian (normal) distribution carry his name.

Why it matters: The Analytical Engine already separated memory (the "store") from processing (the "mill"), the organisation used in computers today.

The design included conditional branching and loops driven by punched cards. The Science Museum in London completed a working Difference Engine No. 2 from his plans in 1991.

Why it matters: Logic gates in the CPU and every condition in an if statement or loop are Boolean expressions; Java's boolean type is named after him.

Boole was largely self-taught and became the first professor of mathematics at Queen's College Cork. Claude Shannon later showed that Boolean algebra describes switching circuits.

Why it matters: Her Note G is often called the first computer program, and she saw that such a machine could process symbols, not only numbers.

She was the daughter of the poet Lord Byron. The programming language Ada (1980) is named after her, and Ada Lovelace Day celebrates women in science and technology.

Why it matters: Moving n discs reduces to moving n − 1 discs twice, the textbook example of a problem whose recursive solution is far simpler than an iterative one.

Lucas also studied the Fibonacci numbers (and gave them that name), the related Lucas numbers, and tests for prime numbers.

Why it matters: His tabulators turned data processing into an industry: input, processing and output on machines.

His Tabulating Machine Company (1896) merged into the Computing-Tabulating-Recording Company in 1911, which was renamed International Business Machines (IBM) in 1924.

Why it matters: The Church–Turing thesis states that anything computable by an effective procedure is computable by a Turing machine (equivalently, in the lambda calculus).

Church reached the result shortly before Turing, by a different method. He supervised Turing's PhD at Princeton (1938). The lambda calculus is the basis of functional programming and of lambda expressions in modern languages.

Why it matters: The CPU–memory organisation taught in Chapter 1, and its "von Neumann bottleneck", carry his name.

He is credited with merge sort (1945), and with Herman Goldstine he introduced flow diagrams for planning programs (1947). He also made major contributions to game theory, quantum mechanics and numerical analysis.

Why it matters: Colossus showed that large numbers of valves could work reliably for digital computation; it was programmable by switches and plugs but did not store its program.

Colossus Mark 1 had about 1,600 valves and Mark 2 about 2,400. The machines were kept secret for decades, so Flowers received little public credit until the 1970s.

Why it matters: She argued that programs should be written in human-readable languages and translated automatically, the idea behind every compiler in the course.

She programmed the Harvard Mark I during the Second World War. Her team's logbook with a moth taped in it (1947) is a famous story about computer "bugs", although the word was already in use. She received the Presidential Medal of Freedom posthumously in 2016.

Why it matters: ENIAC demonstrated large-scale electronic computation; the problems of reprogramming it with cables led directly to the stored-program design.

ENIAC used about 18,000 vacuum tubes and was programmed by setting switches and cables. Their company built UNIVAC I, first delivered to the US Census Bureau in 1951.

Why it matters: A transistor acts as a tiny electronic switch; logic gates and processors are built from millions to billions of them.

Transistors replaced vacuum tubes because they are smaller, faster, cooler and more reliable. Shockley's later company helped start Silicon Valley, and several of its engineers left to found Fairchild Semiconductor.

Why it matters: The Z3 used binary arithmetic and floating-point numbers, ideas central to Chapter 1 and to Java's double type.

The Z3 read its program from punched film and was destroyed in a 1943 air raid. Plankalkül was designed between 1942 and 1945 but published only in 1972.

Why it matters: The universal Turing machine, which reads another machine's rules from its tape, is the theoretical form of the stored-program idea.

During the Second World War he led work on breaking Enigma at Bletchley Park. He designed the ACE computer (1945) and proposed the Turing test (1950). The ACM Turing Award, first given in 1966, is named after him.

Why it matters: The boxes and arrows of flowcharts, used in Chapter 4, descend from these reports.

As an army officer he was the liaison for the ENIAC project and introduced von Neumann to it in 1944. He later directed the IAS computer project and wrote a history of computing, The Computer from Pascal to von Neumann (1972).

Why it matters: His thesis links Boole's logic to the gates inside processors; his 1948 paper made the bit the unit of information.

The word "bit" (binary digit) appears in his 1948 paper, credited there to John Tukey. Information theory underlies data compression and reliable communication over networks.

Why it matters: ASCII's 7-bit codes (A = 65) are the first 128 code points of Unicode and the basis of the character arithmetic used in the course.

ASCII was a committee effort, but Bemer is often called its father. He proposed the backslash in 1961, and was one of the early voices warning about the year-2000 date problem.

Why it matters: The three control structures of Chapters 4, 7 and 8 are enough for every algorithm; goto-style jumps are not needed.

Their result gave the theoretical basis for structured programming, promoted by Dijkstra from 1968. Böhm later did important work on the lambda calculus.

Why it matters: Putting many transistors on one chip made processors, memory and modern computers possible.

Noyce co-founded Intel with Gordon Moore in 1968. Kilby's team also developed the first handheld electronic calculator (1967).

Why it matters: FORTRAN showed that compiled code could be nearly as fast as hand-written machine code, which made high-level languages practical.

He proposed a notation for language syntax that Peter Naur used in the ALGOL 60 report; it is known as Backus–Naur Form (BNF) and is still used to define language grammars.

Why it matters: The pointing and windowing ideas of graphical desktops such as Windows trace back to his work.

His December 1968 demonstration in San Francisco later became known as the "Mother of All Demos". His goal was to use computers to augment human intellect.

Why it matters: Every message on the internet, as shown in Chapter 1, travels as independent packets.

Baran described distributed networks in a series of RAND reports (1964). Davies coined the term "packet" and built a packet-switched network at the NPL in Britain. Their work influenced the design of ARPANET (1969).

Why it matters: BASIC was designed so that students outside science could learn programming, and it became the first language of many home-computer users.

Microsoft's first product was a BASIC interpreter (1975). Kemeny was president of Dartmouth (1970–81); he and Kurtz later founded True BASIC.

Why it matters: Lisp made recursion a normal programming tool and introduced the conditional expression, an ancestor of if–else.

His 1960 paper "Recursive Functions of Symbolic Expressions and Their Computation by Machine" defined Lisp. He also introduced garbage collection and proposed time-sharing.

Why it matters: He argued that programming is a way of thinking about problems, an idea later developed by Jeannette Wing.

Logo's turtle graphics let learners give step-by-step commands and see the result. LEGO Mindstorms robotics kits are named after his book.

Why it matters: Moore's law explains the steady growth in processor power and memory capacity described in the hardware chapter.

He co-founded Intel with Robert Noyce in 1968. The trend held for decades, although it has slowed as transistors approach physical limits.

Why it matters: Writing programs with clear sequence, selection and loops, as in Java, follows his ideas.

He published his shortest-path algorithm in 1959 and introduced semaphores for coordinating processes; his "dining philosophers" problem illustrates deadlock, a topic of the operating systems chapter.

Why it matters: Java's float and double follow IEEE 754, which is why 0.1 + 0.2 prints 0.30000000000000004.

The standard defines formats with sign, exponent and fraction bits, rounding rules, and special values such as infinity and NaN, so the same program gives the same results on different machines.

Why it matters: Quicksort, like merge sort, is a divide-and-conquer algorithm with average running time O(n log n), far faster than bubble sort on large arrays.

He also developed Hoare logic (1969) for proving programs correct and CSP for concurrency. He introduced the null reference in ALGOL W (1965), which he later called his "billion-dollar mistake". He died on 5 March 2026.

Why it matters: Pascal made structured, strongly typed programming the standard in introductory courses for two decades.

His book title Algorithms + Data Structures = Programs (1976) sums up a central idea of this course. He also promoted stepwise refinement: solve a problem by breaking it into smaller steps.

Why it matters: Putting the whole CPU on one chip led to personal computers, phones and the processors described in Chapter 1.

Hoff proposed the architecture, Shima of Busicom worked on the logic design, and Faggin led the silicon design. The 4004 had about 2,300 transistors; Faggin and Shima later designed the Zilog Z80.

Why it matters: Comparing linear and binary search, or bubble sort and merge sort, by counting steps is the method he made standard.

Volume 3 of his series covers sorting and searching in depth. He also created the TeX typesetting system (1978) and promoted "literate programming".

Why it matters: The desktop with windows, icons and menus, which Apple and Microsoft later popularised, grew out of this work.

He is credited with the term "object-oriented" for the approach used in Smalltalk, which influenced Java. His Dynabook concept (1972) imagined a portable computer for children, much like a tablet.

Why it matters: Linux, macOS and Android follow Unix ideas, and the syntax of Java (braces, if, for, while) comes from C.

Thompson also created the B language and, with Rob Pike, designed the UTF-8 encoding (1992). At Google he co-designed the Go language (2009).

Why it matters: The address format user@host is still used for every email address.

Earlier systems let users of the same computer leave messages for each other; Tomlinson extended this across the network. He was inducted into the Internet Hall of Fame in 2012.

Why it matters: Starting a new language by printing a short greeting, as in the Java "Merhaba" program of Chapter 5, is his tradition.

He is the "K" in the AWK language and co-authored several influential books on programming style. The C Programming Language is often called "K&R".

Why it matters: TCP/IP is the "common rule set" that joins networks into the internet, as shown in the layered protocol slides.

IP carries packets between networks using addresses; TCP delivers data reliably and in order. Both are often called "fathers of the internet".

Why it matters: Slide-based presentation software, covered in Chapter 3, became a standard office tool with PowerPoint.

Microsoft bought Forethought in 1987 for about 14 million dollars, one of its first acquisitions, and PowerPoint later became part of Microsoft Office.

Why it matters: Editing a document on screen in the same form as it will be printed, the basic idea of Word, came from Bravo.

He joined Microsoft in 1981 and led its applications group, which also produced Multiplan and Excel. "Hungarian notation" for naming variables is named after him. He travelled to the International Space Station twice (2007, 2009).

Why it matters: The step-by-step DNS lookup in Chapter 1 (root, top-level domain, authoritative server) follows his design.

DNS replaced a single HOSTS.TXT file that listed every computer on the network. It is a distributed, hierarchical database with caching; the RFCs were updated as RFC 1034 and 1035 in 1987.

Why it matters: C++ brought classes and objects to C-style syntax, an approach that Java followed in a simpler, safer form.

The name uses C's increment operator ++, the same operator taught with Java's loops. C++ is widely used for systems, games and performance-critical software.

Why it matters: Rows, columns, cell references and automatic recalculation, the basis of Excel in Chapter 3, start with VisiCalc.

Bricklin had the idea as a Harvard Business School student; Frankston wrote most of the code. VisiCalc made many people buy a personal computer just to run it.

Why it matters: The licensing and open-source topics of Chapters 1 and 2 build on the free-software movement he started.

The GNU General Public License (1989) lets anyone use, study, change and share software as long as modified versions stay under the same terms. Linux systems combine the Linux kernel with GNU tools.

Why it matters: Windows and Microsoft Office, the software of Chapters 2 and 3, come from the company they built.

Their first product was a BASIC interpreter for the Altair 8800. MS-DOS was based on 86-DOS, bought from Seattle Computer Products. The Office suite was first bundled around 1990.

Why it matters: The web is a service running on top of the internet; URLs, HTTP and browsers in Chapter 1 are his design.

CERN made the web technology freely available in 1993, which helped it spread quickly. He founded the World Wide Web Consortium (W3C) in 1994.

Why it matters: Java is the language of Chapters 5 to 12: source code is compiled by javac into bytecode, which the JVM runs on any platform.

The language began in 1991 as Oak in Sun's Green project for consumer devices. Sun was acquired by Oracle in 2010, which now maintains Java.

Why it matters: Python is the course's example of an interpreted (bytecode plus virtual machine) language beside compiled C and hybrid Java.

Python uses indentation to mark blocks instead of braces. He led the language as its "Benevolent Dictator For Life" until 2018.

Why it matters: Her essay is a source of the computational thinking chapter: decomposition, pattern recognition, abstraction and algorithm design.

She has also worked on formal methods; the Liskov–Wing substitution principle (1994) is a rule of object-oriented design. She later headed the computer science directorate of the US National Science Foundation and was a vice president at Microsoft Research.

Why it matters: Linux is the kernel behind Android, most web servers and supercomputers; Chapter 2 separates the kernel from a full distribution.

He announced the project on 25 August 1991 as "just a hobby". In 2005 he created Git, the version control system now used for most software development.

Why it matters: Java's char and String are based on Unicode, so 'A' is 65 and Turkish letters like ğ (U+011F) can be stored and compared.

Becker and Collins worked at Xerox and Davis at Apple; the Unicode Consortium was incorporated in 1991 and Unicode 1.0 appeared that year. UTF-8 (1992), designed by Ken Thompson and Rob Pike, became the dominant encoding.