Anthropic's new AI tool can write 67-year-old COBOL code, sending 115-year-old IBM's stock tumbling by 13% — IBM stock has worst day in 26 years, down 25% MoM and counting

Mainframe
(Image credit: Getty Images)

What do airlines, banks, and insurance companies have in common? Besides being an absolute pain to deal with, they all rely on COBOL and IBM mainframe computers as core infrastructure. The computing giant's stranglehold over those markets may finally begin to crack, though. Anthropic has announced COBOL-specific functionality for its Claude AI bot, and IBM's investors responded with a resounding 13% drop in stock prices.

For practical purposes, COBOL only runs on one type of system, supported by one set of people: IBM's mainframes and its engineers. That means the company has enjoyed multiple decades of telling clients how many zeros the gigantic bills will have tacked on for the next period. The unforgiving nature of that stranglehold means that any attempt at breaking it is most welcome by its existing customers, and a serious threat to IBM as a business.

If you've ever interacted with social security, public administration, healthcare, government, finance, insurance, automotive, retail, or airlines, you've touched a COBOL system at some point in your transaction, even if it was 30 layers deep. Similar to gravity, the language is invisible and yet affects every part of the modern world.

A cynical view of the situation would say that the systems running COBOL are meant to be 100% accurate 100% of the time, a notion that doesn't lend itself very well to the "probabilistically correct" that LLMs can offer. Even still, as I've attested myself, a good bot is a power multiplier in the hands of a competent developer, and can also lower the barrier of entry for young folks trying their hand at wrangling old systems.

The language harkens back to the 1960s, proposing itself as a human-readable language targeted at business transactions, using full decimal-point math as default, in contrast to the default floating-point math in other languages. True to its proposal, it revolutionized business computing, becoming entrenched across almost every sector of note, and was never truly replaced.

The situation doesn't just revolve around IBM's monopoly, though. Most well-versed COBOL programmers are retiring and dying, making their skills rarer and more expensive. The COBOL systems invariably run business-critical operations that cannot afford any downtime whatsoever, and are chock-full of proprietary data formats and business logic that is not documented, and understood only by a few greybeards — if at all.

If you're wondering why COBOL just wasn't up and replaced with something else, know that any rewrite attempt must (a) reverse-engineer miles-long business logic; (b) reverse-engineer the underlying data structures; (c) reimplement said logic and structures while being careful to always use fixed-point decimal math; and (d) execute a perfect transition with minimal to zero downtime.

Even when all those conditions can be true, COBOL systems are often so interconnected that it's unfeasible to replace just the one, as is the case with airlines. And heaven help you if you're in the financial sector, as you'll have to undergo extremely long-winded tests and audits, adding months to any deployment.

There's a well-known joke among programmers that almost certainly originated from COBOL: "When I wrote this code, only God and I understood what it does. Now... only God knows."

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Bruno Ferreira
Contributor

Bruno Ferreira is a contributing writer for Tom's Hardware. He has decades of experience with PC hardware and assorted sundries, alongside a career as a developer. He's obsessed with detail and has a tendency to ramble on the topics he loves. When not doing that, he's usually playing games, or at live music shows and festivals.

  • American2021
    "Most well-versed COBOL programmers are retiring and dying, making their skills rarer and more expensive. The COBOL systems invariably run business-critical operations that cannot afford any downtime whatsoever, and are chock-full of proprietary data formats and business logic that is not documented, and understood only by a few greybeards — if at all... There's a well-known joke among programmers that almost certainly originated from COBOL: 'When I wrote this code, only God and I understood what it does. Now... only God knows.'"

    "Code Translation Is Not Mainframe Migration: This is the part the market seems to fundamentally misunderstand... Translating COBOL to Java is one step in an enormously complex process. Moving off the mainframe and midrange systems that drive IBM's revenue requires far more than code conversion. It requires migrating the data layer, including decades of accumulated business data in formats tightly coupled to the mainframe environment. It requires replacing or replicating the middleware, transaction processing, and job scheduling infrastructure that these systems depend on. It requires re-engineering the integration points with every upstream and downstream system that touches the mainframe. It requires re-creating the operational procedures, disaster recovery capabilities, and security controls that enterprises have built around these platforms over decades" -Michael Stricklen (published 02/24/2026).
    Reply
  • Gururu
    I guess this is what AI is for. To do the dirty jobs that the new kids don't want to do anymore. Like picking strawberries.
    Reply
  • johnrock2
    Interesting. I just asked Gemini 3 flash to write a program in COBOL that calculates pi to 10 digits. It had no problem and even explained what each part did:

    IDENTIFICATION DIVISION.
    PROGRAM-ID. PI-10-DIGITS.
    AUTHOR. GEMINI-AI.

    DATA DIVISION.
    WORKING-STORAGE SECTION.
    * 'V' represents a virtual decimal point.
    * 9(1)V9(10) means 1 digit before and 10 after the decimal.
    01 PI-RESULT PIC 9(1)V9(10) VALUE 0.
    01 WS-CONSTANTS.
    05 WS-FOUR PIC 9(1) VALUE 4.

    PROCEDURE DIVISION.
    MAIN-LOGIC.
    DISPLAY "CALCULATING PI USING BUILT-IN ARC-TANGENT..."

    * Most modern COBOL compilers (like GnuCOBOL) support
    * intrinsic functions for trigonometry.
    COMPUTE PI-RESULT = 4 * FUNCTION ATAN(1).

    DISPLAY "PI TO 10 DECIMAL PLACES: " PI-RESULT.

    STOP RUN
    .
    Reply
  • Gururu
    I think they are offering Claude now for deeper end analysis and modernization of existing systems while Gemini itself identifies its own limitations to:
    "It is generally less capable in COBOL compared to popular languages and may struggle with the complex, large-scale, and system-specific nuances of legacy systems."
    Claude seems to be getting a lot of positive press these days.
    Reply
  • Arkitekt78
    And I'm certain its results are amazingly accurate and blindly usable. 🤣
    Reply
  • MickeyWhite
    Admin said:
    IBM stock takes a 13% whiplash after Anthropic announces COBOL AI tooling

    Anthropic's new AI tool can write 67-year-old COBOL code, which sends 115-year-old IBM's stock tumbling by 13% — IBM stock has worst day in 26 year... : Read more
    Cobol is still being used because it works.
    But you can learn and run cobol on Windows/Linux/Mac. GnuCOBOL is free and open source.
    Reply
  • JamesJones44
    The guys in their 70s making 500k a year because no one else knows the software and the only ones left that can still tolerate the language can finally retire!
    Reply
  • JamesJones44
    johnrock2 said:
    Interesting. I just asked Gemini 3 flash to write a program in COBOL that calculates pi to 10 digits. It had no problem and even explained what each part did:

    IDENTIFICATION DIVISION.
    PROGRAM-ID. PI-10-DIGITS.
    AUTHOR. GEMINI-AI.

    DATA DIVISION.
    WORKING-STORAGE SECTION.
    * 'V' represents a virtual decimal point.
    * 9(1)V9(10) means 1 digit before and 10 after the decimal.
    01 PI-RESULT PIC 9(1)V9(10) VALUE 0.
    01 WS-CONSTANTS.
    05 WS-FOUR PIC 9(1) VALUE 4.

    PROCEDURE DIVISION.
    MAIN-LOGIC.
    DISPLAY "CALCULATING PI USING BUILT-IN ARC-TANGENT..."

    * Most modern COBOL compilers (like GnuCOBOL) support
    * intrinsic functions for trigonometry.
    COMPUTE PI-RESULT = 4 * FUNCTION ATAN(1).

    DISPLAY "PI TO 10 DECIMAL PLACES: " PI-RESULT.

    STOP RUN
    .
    I really hate reading COBOL, I took it in college for fun (dumb idea) and hated it. I found it less readable than Fortran (also took for fun) even though Fortran is older than COBOL and in some cases found COBOL more annoying than Assembler (6800 anyway). Of course they are all terrible compared to C/C++, Rust, Java, etc. but was trying to keep my comparison to era appropriate languages.
    Reply
  • FleshharrowerX
    johnrock2 said:
    Interesting. I just asked Gemini 3 flash to write a program in COBOL that calculates pi to 10 digits. It had no problem and even explained what each part did:

    IDENTIFICATION DIVISION.
    PROGRAM-ID. PI-10-DIGITS.
    AUTHOR. GEMINI-AI.

    DATA DIVISION.
    WORKING-STORAGE SECTION.
    * 'V' represents a virtual decimal point.
    * 9(1)V9(10) means 1 digit before and 10 after the decimal.
    01 PI-RESULT PIC 9(1)V9(10) VALUE 0.
    01 WS-CONSTANTS.
    05 WS-FOUR PIC 9(1) VALUE 4.

    PROCEDURE DIVISION.
    MAIN-LOGIC.
    DISPLAY "CALCULATING PI USING BUILT-IN ARC-TANGENT..."

    * Most modern COBOL compilers (like GnuCOBOL) support
    * intrinsic functions for trigonometry.
    COMPUTE PI-RESULT = 4 * FUNCTION ATAN(1).

    DISPLAY "PI TO 10 DECIMAL PLACES: " PI-RESULT.

    STOP RUN
    .
    My right eye twitched reading that, when I was at college in the 80's - my cobol professor-person would freak out when we didn't use the correct identing. I just googled it, at least this is no longer a requirement in modern compilers.
    Reply
  • johnrock2
    FleshharrowerX said:
    My right eye twitched reading that, when I was at college in the 80's - my cobol professor-person would freak out when we didn't use the correct identing. I just googled it, at least this is no longer a requirement in modern compilers.
    When Gemini 3 flash gave me the code the indents were there. When I pasted and posted them as part of my comment the indent got stripped away. Just wanted you to know the AI at least got that part right!
    Reply