CWI is older than the computer science it became famous for. Six Dutch mathematicians founded it in February 1946, in a country still rebuilding from the war, and called it simply the Mathematisch Centrum. The mission was practical to the point of life-or-death: build the mathematical models the Netherlands would need to defend itself from the sea. The Delta Works, the vast post-1953 flood barrier system, drew on Mathematical Centre calculations. So did the wings of the Fokker F27 Friendship, the turboprop that Dutch readers in 2006 voted the most beautiful Dutch design of the twentieth century. The institute's earliest work was, in the truest sense, mathematics for a country that lay below sea level.

Computer science arrived through one man. Adriaan van Wijngaarden, who would later be called the founder of Dutch informatica, became director and ran the place for nearly twenty years. He brought in a young Edsger Dijkstra, who did most of his early work on algorithms and formal methods at CWI - shortest paths, structured programming, the long argument that software could be reasoned about as rigorously as a theorem. The first Dutch computers, the Electrologica X1 and X8, were designed in the same building, then spun off into a company that manufactured them. Van Wijngaarden built Algol 60 and Algol 68 with international committees that met partly at CWI. The grammar he developed to describe Algol 68 still carries his name.

On 1 May 1986 a researcher named Piet Beertema, working from CWI, registered cwi.nl. With that single record .nl became the first country-code top-level domain outside the United States to go live. For the next decade Beertema, almost single-handedly, ran the entire Dutch internet's domain administration from his office. On 17 November 1988 he opened a TCP/IP link from CWI to the NSFNET in the United States - one of only two such European connections, shortly after France's INRIA. For practical purposes, the European internet started in two places at almost the same moment, and one of them was a math institute in Amsterdam. When the domain registry grew too large for one researcher, CWI spun it off as SIDN, which still runs .nl today.

And then there was Guido. Van Rossum had been part of the ABC team at CWI, an attempt to build a programming language that ordinary people - not just professional engineers - could actually learn. ABC did not catch on. Python, the side project he started over the 1989 winter break, was meant to be its successor: readable, batteries-included, friendly to beginners but powerful enough to do real work. The institute let him run with it. He posted the first public release in February 1991. Three decades later Python runs scientific computing, machine learning, web back-ends and most of the data science people learn in their first college course. Google built much of its early infrastructure on it. The language that came out of a quiet Dutch math institute is now arguably the most widely taught programming language on Earth.

The institute has never stopped spinning things off. David Chaum founded DigiCash from a CWI office in 1990 - an early attempt at anonymous electronic money that predates Bitcoin by almost two decades. MonetDB came out of CWI's database group in 2008 and rewired how columnar analytics worked. DuckDB Labs spun out in 2021 to commercialize a database now embedded in countless data pipelines. In February 2017 CWI researchers, working with Google, announced the first practical collision attack on the SHA-1 hash function, accelerating its retirement from secure systems worldwide. The building still looks like a university math department - blackboards, coffee, the small posters announcing seminars on graph theory. The work that happens inside has a habit of escaping into the wider world and changing it.