Algorithms are older than computers by about two thousand years. The sequence of ideas runs from arithmetic procedures written on clay tablets and papyrus, through Ada Lovelace’s notes on a machine that was never finished, to the sorting, graph and cryptographic algorithms of the 1940s to 1970s, and then to large-scale data processing and machine learning. This post is a timeline of that path with dates that have been checked, and a note on why each step still matters to programmers today.<\/p>\n
The word algorithm<\/em> comes from the name of Muhammad ibn Musa al-Khwarizmi, a scholar working in Baghdad in the early 9th century, whose book on calculation with Hindu-Arabic numerals was translated into Latin and spread those methods through Europe. The oldest well-documented procedures are far older:<\/p>\n Euclid’s method and the sieve are still taught, and still used as building blocks. Both fit in a few lines of Python:<\/p>\n The sieve runs in roughly O(n log log n) time, and Euclid’s algorithm takes a number of steps proportional to the number of digits. Neither has been replaced in 2,000 years for its job. The Babylonian square-root method also survives: it is Newton’s method applied to In the 1830s Charles Babbage designed the Analytical Engine, a mechanical general-purpose computer with a store, an arithmetic unit and punched cards for instructions, an idea taken from the Jacquard loom. It was never completed. In 1843 Ada Lovelace published English notes on the engine that included, in the long Note G, a detailed method for computing Bernoulli numbers. It is often called the first published computer program. Because the machine did not exist, the program was never run on it; what matters is that it separated the procedure from the machine.<\/p>\n The first high-level languages (FORTRAN in 1957, LISP and ALGOL in 1958) let people write algorithms in something close to mathematical notation. ALGOL in particular was designed to describe algorithms, and its block structure influenced most later languages.<\/p>\n Until the 1970s, secret communication required sharing a key in advance. Public-key cryptography changed that: RSA (1977) lets anyone encrypt with a public key while only the owner can decrypt. DES became a US federal standard in January 1977 and was superseded by AES, published in 2001 and adopted as the replacement in 2002. The security of RSA depends on factoring large numbers being slow with known classical algorithms. Shor’s quantum algorithm (1994) would factor efficiently on a large enough quantum computer, but as of October 2026, demonstrations on real hardware have only factored very small numbers like 15 and 21, which is why standards bodies are moving to new post-quantum schemes as a precaution rather than because RSA is broken today.<\/p>\n The trend is visible: early algorithms were about exact answers on tiny machines; later ones trade exactness for scale (hashing, sketches, approximate nearest neighbours) or learn their behaviour from data.<\/p>\n If you want to try the techniques named here, the Merge Sort<\/a>, Binary Search<\/a> and Quick Sort<\/a> lessons let you implement them step by step, and our post on algorithm design patterns<\/a> explains the strategies behind them.<\/p>\n","protected":false},"excerpt":{"rendered":" A dated timeline of algorithms, from Euclid and al-Khwarizmi to Babbage, early computers, sorting, graphs, cryptography and machine learning, with working code.<\/p>\n","protected":false},"author":1,"featured_media":1830,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[23],"tags":[],"class_list":["post-1831","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-problem-solving"],"_links":{"self":[{"href":"https:\/\/algocademy.com\/blog\/wp-json\/wp\/v2\/posts\/1831"}],"collection":[{"href":"https:\/\/algocademy.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/algocademy.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/algocademy.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/algocademy.com\/blog\/wp-json\/wp\/v2\/comments?post=1831"}],"version-history":[{"count":1,"href":"https:\/\/algocademy.com\/blog\/wp-json\/wp\/v2\/posts\/1831\/revisions"}],"predecessor-version":[{"id":8683,"href":"https:\/\/algocademy.com\/blog\/wp-json\/wp\/v2\/posts\/1831\/revisions\/8683"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/algocademy.com\/blog\/wp-json\/wp\/v2\/media\/1830"}],"wp:attachment":[{"href":"https:\/\/algocademy.com\/blog\/wp-json\/wp\/v2\/media?parent=1831"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/algocademy.com\/blog\/wp-json\/wp\/v2\/categories?post=1831"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/algocademy.com\/blog\/wp-json\/wp\/v2\/tags?post=1831"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}\n
n \/ guess<\/code>.<\/li>\ndef gcd(a, b):\n while b:\n a, b = b, a % b\n return a\n\ndef sieve(n):\n is_p = [False, False] + [True] * (n - 1)\n for i in range(2, int(n ** 0.5) + 1):\n if is_p[i]:\n for j in range(i * i, n + 1, i):\n is_p[j] = False\n return [i for i, p in enumerate(is_p) if p]\n\nprint(gcd(1071, 462)) # 21\nprint(sieve(30)) # [2, 3, 5, 7, 11, 13, 17, 19, 23, 29]<\/code><\/pre>\nx\u00b2 = n<\/code>, and a handful of iterations gives about fifteen correct digits for 2 (1.414213562373095 after five).<\/p>\nThe mechanical era: Babbage and Lovelace<\/h2>\n
The electronic era: the first programs on real machines<\/h2>\n
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sorted<\/code> uses Timsort, a hybrid of merge sort and insertion sort.<\/li>\nGraphs, data structures and storage (1950s to 1970s)<\/h2>\n
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Cryptography: algorithms that need to stay hard<\/h2>\n
Web scale and machine learning (1990s to now)<\/h2>\n
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What programmers should take from the history<\/h2>\n
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