CWI preserves historic punched tape collection

Tiny holes on strips of paper once held entire programs and documents. Thanks to the efforts of CWI staff and volunteers, these early computing artifacts are now digitized and accessible online.

Publication date
9 oct 2025
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Punched tape was a key medium for programming and storing data in the 1950s and 1960s, long before USB sticks or hard drives existed. Today, CWI preserves its own historic tapes from the Mathematisch Centrum (now CWI), including materials used on early Dutch computers such as the Electrologica X1.

The project, led by CWI Fellow and emeritus professor Paul Klint together with Geert Rolf, intern at MC back in 1980/1981, involved reading, decoding, and archiving over 160 tapes. Last winter (2024-2025), the tapes were read on Geert’s PDP-11/10, on a hayloft at his former private computer museum, the ‘Tehuis voor Bejaarde Computers’ (‘Home for Elderly Computers’). The rolled tapes required careful handling, and rolling them back by hand after reading took several minutes each - 160 times over.

Rolled-up punched tape in the PDP-11. A roll of punched tape being read on Geert Rolf’s PDP-11/10, as part of the project to digitize and preserve CWI’s historic tape collection. Picture: Geert Rolf.
Rolled-up punched tape in the PDP-11. A roll of punched tape being read on Geert Rolf’s PDP-11/10, as part of the project to digitize and preserve CWI’s historic tape collection. Picture: Geert Rolf.

In spring, the tapes were returned to CWI during a small celebration with then-director Ton de Kok and Vera Sarkol, head of the library that archives the tapes. They have now been made fully online accessible for study in the CWI repository.

Punched tape project: CWI Fellow Paul Klint, then-CWI director Ton de Kok, Geert Rolf and Vera Sarkol (CWI Library), 10 April 2025. Picture: CWI/P. Roberts.
Punched tape project: CWI Fellow Paul Klint, then-CWI director Ton de Kok, Geert Rolf and Vera Sarkol (CWI Library), 10 April 2025. Picture: CWI/P. Roberts.

Paul Klint says:

Preserving these tapes is about more than just the data. They are part of the history of computing at the Mathematisch Centrum and a unique resource for researchers, students, and anyone interested in the roots of programming.

Geert Rolf adds: “The 7-hole tapes from the FlexoWriter contained readable Algol 60 programs or text documents, while the 5-hole binary tapes required careful conversion. Some of the larger or damaged tapes simply could not be read, so we prioritized the ones that could be safely handled.”

The digitized collection includes both FlexoWriter and binary tapes, spanning programming languages, assembler code, and text documents. While the tapes themselves were already digital in nature, the process of making them accessible for study required meticulous technical work and specialized tools.

CWI director Vanessa Evers says:

This project offers a rare peek into the dawn of computing at the Mathematisch Centrum. It’s like opening a time capsule of a day in the life of a researcher all those years ago - a joy not only for historians of science, but for anyone who loves imagining the past and the future of programming and computer design.

"For students, these digitized punched tapes could also offer hands-on material for short research projects that connect today's computing with its earliest roots," Paul Klint adds.

The digitized tapes, along with documentation of the programs used for decoding and conversion, are freely available in the CWI repository.

More information

More information and links to the repository can be found on the CWI punched tape collection web page.

Research

Are you interested in studying these files in a brief project for master students? Please contact Paul Klint.