FORTRAN Milestone On This Day

Written by Mike James Sunday, 21 September 2025 The very first successful FORTRAN program ran on September 20, 1954. Invented at IBM by a group led by John Backus, FORTRAN, standing for “FORmula TRANslator” was to first language to crack the problem of converting mathematical expressions to code.

From today’s perspective the idea that the same computer language can be used on a variety of hardware is taken for granted. That was not the case back in the 1950s when every new computer had its own language - machine code tied to the architecture of the machine and designed to make the best of its features. A programmer would know how the machine worked and would carefully craft code to achieve a result that took minimum time and/or memory. Every byte was manually allocated and managed and so was the use of the machine’s internal registers where the work was done. The big problem is that working in machine code is particularly unfriendly and makes creating programs time-consuming and error-prone.

To enable the move away from machine code and to enable a computer language to run on multiple machines needed a compiler. This was the breakthrough made by IBM for its 704 computer.

The IBM 704 - first with FORTRAN

The project undertaken by a team under the leadership of John Backus, was to devise a computer language that could compile any arithmetic expression. To do this they had to invent a way of writing down and making use of the rules of grammar for mathematical expressions. The trick was to convert the expression into a syntax tree which makes clear the relationships between the operators and their priorities. Once you have the syntax tree then you can use it to generate the operations in the correct order by simply “walking” the tree. For a more detailed explanation see: Grammar and Torture.

This task was expected to take six months, and the first successful FORTRAN program, was run with the original timescale. However, it was another two years before the first compiler was available and it took until April 1957 before a working compiler was distributed to customers. It consisted of 25,000 lines of machine code on a magnetic tape and, complete with bugs, it became part of every IBM 704 installation.

FORTRAN revolutionized programming and made IBM the number one computer company for decades. It introduced many new ideas - arithmetic assignment, comments, the DO loop, subroutines and functions, formatted input/output - to name just a few. It also seeded the idea of machine independence because a machine that had a FORTRAN compiler could run any FORTRAN program.

As the first high level language FORTRAN is clearly important but it also influenced many generations of programmers, especially when you take into account the popularity during the early home computer era of BASIC, which was derived directly from it.

Every single language that compiles an expression owes a debt to FORTRAN and to John Backus.

It would be wrong to consider FORTRAN as a purely legacy language. It is still used by scientists and engineers and continues to evolve.

It was Fortran 90, which dispensed with the all-caps name that marked the transition to Modern Fortran. A major modernization of the language, it introduced “free-form” source code, which freed programmers from the column restrictions and allowed for more readable code. Later Fortran 2003 added features for Object-Oriented Programming (OOP), such as type extension, inheritance, and type-bound procedures. It also introduced standardized C interoperability, making it easier to integrate Fortran with other languages. In Fortran 2008 the main focus was on native parallel programming with the introduction of coarrays. whch provide a built-in, simplified way to write code for parallel systems (like supercomputers) without relying solely on external libraries.

Fortran 2018 expanded upon previous standards, particularly in C interoperability and parallel programming and is considered a clearer standard that has allowed many deficiencies and irregularities in the earlier language versions to be resolved. The most recent version, Fortran 2023, continued the trend of adding features that make the language more robust and convenient for its core user base.

The fact that Fortan is still relevant is reflected in the fact that is currently at #10 in the TIOBE Index which ranks computer languages in terms of their popularity. When it re-entered the Top 20 in April 2021 it was greeted with a degree of surprise that a “dinosaur” could be back after an absence of more than 10 years but it contined to rise and re-entered the Top 10 in May 2024, reaching its highest ever position since 2001 at #8 in November 2024.

• Mike James is the author of ***The Programmer’s Guide To Theory***which sets out to present the fundamental ideas of computer science, including the grammar used by a compiler, in an informal and yet informative way.

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Last Updated ( Sunday, 21 September 2025 )