How Tanenbaum’s Textbook and PDP-11 Labs Sparked a Trilingual Computing Breakthrough

Enjoying 'C' programming on a vintage PDP-11 terminal in the University of Essex lab, 1984 (Source: Image © Turrance Nandasara)

A Journey Through Computer Science

Structured Computer Organisation by Andrew S. Tanenbaum was my first formal textbook in computer science. Both the second (1984) and third (1989) editions offered a rich exploration of operating systems and computer architectures, making them indispensable resources for students in the early 1980s.

The second edition, published in 1984, introduced me to the hierarchical structure of popular microprocessors such as the IBM 370, PDP-11, and MC68000. It also covered the UNIX and CP/M operating systems and included ready-to-run 'C' and PASCAL programs—bridging theory with hands-on practice.

“I still remember the hum of the PDP-11 lab, the thrill of compiling my 'C' programs, and the quiet power of Tanenbaum’s words.”

During my time at the University of Essex in 1984, I worked extensively with the PDP-11 and CP/M operating system while studying Pascal, PROLOG and C programming. These experiences laid the groundwork for my deeper understanding of system-level computing.

University of Essex, Colchester, UK. 1984

Taken in 1984 at the University of Essex, this image shows me standing before the Administration Block, framed by the student dormitories that formed the backdrop of my early academic life. (Source: Image © Turrance Nandasara)

Structured Computer Organisation: The textbook that launched a legacy.

“Tanenbaum’s clarity and structure made the invisible layers of computing feel tangible and navigable.” (Source: Image © Turrance Nandasara)

The third edition, released in 1989, expanded the scope of operating system concepts. It introduced advanced topics, including virtual memory, multitasking, and the fundamentals of distributed systems. UNIX was presented as a case study, offering practical insights into OS design.

This edition also featured updated examples from Intel’s 8088/80286/80386 processors and Motorola’s 68000/68020/68030 family. As in the earlier edition, Tanenbaum meticulously explained the five levels of computer organisation:

• Digital logic level

• Microprogramming level

• Conventional machine-level

• Operating system machine level

• Assembly language level

These layers became more than academic—they became tools for innovation.

Localising Technology in Sri Lanka

While at the University of Colombo, I applied the principles from Tanenbaum’s third edition to develop SBIOS (Sinhala Basic Input/Output System) and TBIOS (Tamil Basic Input/Output System)—custom BIOS replacements written in Assembly language for IBM-compatible systems.

This was a landmark achievement:

• Enabled trilingual computing in Sinhala, Tamil, and English

• Marked the first use of localised IBM PCs by the Sri Lankan community

• Empowered users to interact with technology in their native languages

Localised BIOS powering Sri Lanka’s first trilingual PCs (Source: Image © Turrance Nandasara)

Supporting this development were the IBM PC/XT and PC/AT reference manuals, which provided essential technical guidance for working with the 8088/80286/80386 processor families.

Originally developed in the late 1980s, the ‘Wadantharuwa’ package was marketed as a pioneering solution within the IBM PC environment. (Source: Image © Turrance Nandasara)

The image illustrates the Sinhala BIOS (SBIOS) functioning within an IBM PC setup, with the DOS prompt actively handling user input and system output in the Sinhala language character set. (Source: Image © Turrance Nandasara)

Reflections on a Cross-Continental Journey

From lecture halls in the University of Essex to development labs in Colombo, my journey through computer science was shaped by Computer Science textbooks, a handful of processors, and a vision for inclusive technology. What began as academic curiosity evolved into a mission: to make computing accessible, multilingual, and locally relevant.

“From Essex to Colombo, my journey wasn’t just about mastering machines—it was about making them speak our languages.”

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